Alright so all that setup is well and good, but how about we play the damn game?
I hear your concerns. I've loaded up a game of Civ, gathered a bunch of screenshots, and I'll talk around that unlike the ton of text of part 1. Though keep in mind first:
Here I've loaded into the game as Brazil. Although not a Civilization that takes into account special resources, its unique improvement emphasizes jungle placement (and overall, not cutting it down). Before that, I would be wise to address two things:
1 - A MAJOR, but common mistake: Do not move with your settler first. Especially in my scenario, moving my Settler anywhere but southeast by one tile would end my turn. The best thing to do when you immediately load into the game is explore with your warrior before committing to that with your settler. Maybe you find a better spot for your capital to be placed? Maybe you don't. The point is, you don't take that chance with your settler, you do it with your warrior. In my case, however, I didn't notice anything with my warrior but still ended my turn before founding my capital on the next turn. More on that later.
2 - Why does my game look different from yours? This is simply due to a change to my user interface (UI) called "Enhanced UI" (descriptive I know). Though it truly helps, it gets me quite easy access to things that should be normally accessible but just isn't. It may seem a lot more complicated than the default, but I'd actually argue not having something like this can make the game harder. If you'd like to download it, you can find it here.
Unless you're the Huns, there is no way to tell whether you're near spots of Iron or Horses, if you are playing as a Civ which requires one of the two resources. Luckily for you, that's just gonna have to be a problem for your future cities to figure out, let's look at the capital first. There are three things you would like to look out for when you found a capital, those being:
1 - Luxury Resources: Unlike Strategic Resources like Iron and Horses, you are able to see Luxury Resources immediately. In the above screenshot, those can be identified as Salt and Cocoa. You don't need to go out of your way to settle right next to them as your natural border expansion should eventually get to them, but be somewhat near.
2 - Terrain: Every Civilization has their own sort of "starting bias". In Brazil's case, they will often spawn next to Jungle as it is a very crucial part to their unique improvement. In this case, you likely should go out of your way to make sure you're settling around terrain that benefits you if it does, but do not settle directly on it as you cannot work the capital tile with your worker.
3 - Water Sources: There are three to look out for: Coast, Lakes & Rivers. Settling near Coast tiles will allow your city to be able to build naval units and buildings, though are generally useless tiles for your city to use unless there are luxury resources, fish, or atoll on those tiles. You should probably have at least one coastal city, but that does not have to be your capital.
Lakes and Rivers are VERY important. Lakes look just like coast tile, except they only occupy a few tiles in-land. If you're having trouble figuring whether a tile is Coast or Lake, hover your mouse over it for a couple seconds and a description should pop up. Rivers, can be a bit subtle but with forest/jungle-less tiles, should be able to spot. Why is this in a different section? Because I would strongly recommend settling near them. Certain buildings such as the garden can only be built in cities next to rivers. They often have land very good for population growth near it as well. It may be a pain to cross, but once you discover Engineering, you'll be able to build bridges to make this less of a hassle.
Point is, if you see lake or rivers, that is likely a priority spot for your capital.
In the above screenshot, I founded my capital on the second (1st in game-time) turn. I did this as:
1 - The spot I moved my settler to had a river next to it
2 - The spot I moved my settler to had lots of jungle around it
The Salt and Cocoa are not in my immediate territory, but in time I will have all three of what I was looking for within my capitals borders. Maybe I could have been a little better in moving my capital more near the coast to the east of this location, but I did not want to spend more than 1 turn in founding my capital.
Assuming you've done the same, you're now tasked with building your first units/buildings as well as picking your first science option. Let's get the easy one out of the way:
90% of the time, I would recommend you build a scout first. Unless you are playing a Civ which has their unique building replace the monument or warrior, scouting takes priority first. Even if you are a Civ who has those conditions, it's still a toss-up on whether you should go with that or the scout first. Briefly, I'll say that only the Aztecs and maybe Ethiopia can go without immediate Scout.
After building a scout, usually, the next order of business is building a monument so you can get to social policies sooner. After those two are done it's just a matter of the win type you are going for:
Cultural Players: A lot of cultural Civs have a lot to do with establishing religion, so this would be the time to get your Shrine.
(Certain) Domination Players: If you have a unique unit that replaces the Warrior or Archer (and discovered the technology) you could maybe get a headstart on producing those units.
Everyone Else: The Worker is probably your best bet. You'll want happiness before you build new cities, and you can't acquire happiness in the early game without 1) discovering natural wonders or 2) improving luxury resources. The 2nd one is the easier one to come by.
However, if you're a scientific player specifically, you may want to get to building your Library as soon as possible. What I would do, is what I call "pre-loading" a unit, where you work on a unit up until a certain technology becomes available, and immediately switch production to that new unit/building. In this case, immediately switch production to the Library as soon as you discover Writing, and once that's done you can resume working on your worker without the loss of progress. You could also do this strategy with a settler, but once again keep your happiness in mind (more on this later).
Hey! If you've downloaded the same UI as me, this may look daunting. Luckily for you, I will just simply break this down in "scientific priority".
1 - If you have a unique unit that requires horses: Start off with Animal Husbandry. You're going to want to settle your future cities around Horses to be able to take advantage of that unit. How else are you gonna know where horses are, without researching the technology to be able to find and utilize them?
2 - If you have a unique unit that requires iron: Start off with Mining, and then immediately go towards Bronze Working after that. This is for the same reason as the step prior, except it takes a little bit more time with two technologies required instead of one.
3 - Pottery: If you don't have this problem or have already researched your necessary technologies beforehand, Pottery leads into a lot of helpful things. If you're looking to start a religion, the Shrine immediately helps. If not, you are on your way into Writing/Calendar/Sailing. Writing helps your Civ create the Library and get a start on your science gain (important for Science Civs). Calendar allows your workers to work a lot of luxury resources, in my own example, I would need this technology (along with Bronze Working, to cut down Jungle) to be able to use my Cocoa. Finally, Sailing offers you access to the Trireme as well as Work Boats, being able to explore coastlines and work sea resources respectively.
4 - Otherwise: I would probably say of the remaining technologies, Trapping may be the most helpful though the other ones are dependent from Civ to Civ. Are you near Marble or Stone? Get Masonry as soon as you can. Have a unique unit that replaces the Archer? Get to Archery sooner rather than later! Absolutely tired of how slow it takes you to move between cities? You'll need The Wheel. It's up to your judgment.
Just in general, after being able to see the strategic resources you require, researching "worker technologies" is your priority. Outlined all of that in Pottery, but this overall refers to Calendar/Sailing/Masonry/Trapping. Luxury resources are a HUGE part to your game.
Skipping ahead a few turns to when I have built my scout, there are three things you need to look out for. In priority:
1 - Ancient Ruins: As seen above right next to those Barbarians, Ancient Ruins are a crucial part to the early game. They can allow you bonuses such as free culture, gold, population, etc., all worth exploring for. Getting off to a good start means exploring as many ancient ruins as possible, which is why you should build a scout as soon as possible for easy navigation. Warriors can of course, do this too, but they suffer movement penalties from rough terrain (Forest/Jungle, Hills, crossing rivers, entering marsh). Don't spend too much time scouting with your warrior, so that you can defend your own capital (and later, its workers).
2 - City States & Other Civs: City States will likely be the bulk of your trade routes to acquire more gold, as well as other benefits like extra Happiness, "free" military units, and much later, votes in the United Nations & World Congress. As for finding other Civs, it's more about knowing where they are if they are an aggressive Civ that plans to invade, but otherwise provides more detailed trading so that you can gain more happiness acquiring their luxury resources, and maybe trading some of your own.
3 - Future City Locations: Of course, Scouting reveals more of your map which you'll eventually use to settle more cities if you're smart. The amount can vary depending on your playstyle and victory condition, but you should still at least settle 1 more city (provided you're not Venice). The same things apply as I said in my Capital Section, but now with two more considerations:
Strategic Resources: By the time you want to settle your second city, you should probably be able to see Horses and Iron. Much later down the line, you'll also want to take into consideration Coal, Oil, Uranium & Aluminum. Settle as close to these resources as possible if you require it, and if you don't they are still probably very nice to get. Uranium especially, you don't want to get into the wrong hands.
Natural Wonders: This wasn't in the capital section because it is a VERY low chance you spawn right next to a Natural Wonder. Though if you see a Natural Wonder without any cities around it, make it your priority to send a Settler there as soon as possible. A lot of them have to do with faith gain, but you can gain food, gold, production & science at great amounts for the early game if you settle right next to it.
There's gonna be a lot of text here, but it's for a good reason as there are multiple things to address. In general, you should have at least a 2nd city. Relying everything on your capital is a bad idea unless you're Venice whose playstyle specifically runs around only having one city.
Next, you need to consider building "Tall" or "Wide".
Building Tall - Building Tall refers to having between 1-4 cities that focus on having high populations. High populations mean quicker production, more efficient research & culture gain, but comes at the drawback of only being able to build a small number of things at a time. Faith and sometimes even tourism can have a hard time being generated with a small number of cities too. If you're going for a Scientific Victory or (often) a Cultural Victory, you should build tall. It can work with Diplomatic Civs, though don't even bother as a Domination Civ.
Building Wide - Building Wide refers to having a whole bunch of cities which span the entire map to collect resources, usually at the cost of efficiency. Pretty much take the reverse of everything I said with building tall, and also know that wide building corresponds to a lot more work in management. Diplomatic Civs can benefit building wide for the sake of acquiring lots of resources to be used in trade for gold acquisition. Domination Civs benefit from both acquiring required resources and more or less unintentionally build wide via conquering anyways. Cultural Civ is more of a mixed bag, as you'll not be a very efficient culture-generating Civ to start, but it can really get going in the late-game provided you play your chips right to generate both Tourism and Faith before it. You should not build wide during a science victory though.
This section is called "Should I do it?" for a reason though, so let's get into that. First of all, you should try to build your cities sooner rather than later regardless of building tall or wide. You want to give your cities as much time to develop in the early game, so they can be just as strong as your capital in the late game. At the same time, you don't want to build cities to the point where you severely slow yourself down in that early stage. So keep in mind two things:
1 - Happiness Matters: Notice that with every population point your capital grows, your happiness also goes down? Well, you don't want to let that go into the negatives. An unhappy empire means a great loss of efficiency, and one of the best ways to cause unhappiness is by building more cities than necessary. A nice rule of thumb is that if your city has at least 3 happiness, you're all clear to settle a new city but less than that and you're getting into dangerous territory in a matter of turns. Though pro tip, if you're playing as Indonesia and you settle a new "continent" (any sort of tile that's off of your own continent + other continents you've already settled) the free luxury resource will cover your unhappiness.
2 - Don't Neglect Buildings: You should try to build a Library as soon as you can. You should not ignore your unique buildings if you have access to them early enough. Some Civs benefit quite a lot from religion, so building a Shrine ASAP would be a wise decision. The point is, if you building a Settler for another city is holding you back from acquiring necessary buildings, do not build another settler.
The reason for me pushing this section to the end is because of needing the "Tall vs Wide" terminology. Social Policies despite being tied to culture, are very helpful to every Civ in the game no matter what they are going for. Adopting policies gives you minor boosts to things that Civs can require, from free units to curbing unhappiness. This is why you should never completely neglect culture: build a monument in every city that you can!
But... This is an ancient era guide. What do we start with? Luckily for you, it's usually a matter of Tradition vs Liberty.
Tradition: If you are a Civilization that builds tall, Tradition is your best bet. It gives your capital a free +3 culture per turn which helps knock this tree down quite early. In the specifics, Aristocracy helps with your cities that reach 10 population and gives you an early boost to Wonder building, making it very useful for Cultural players as well as Science players (Great Library is a must). Legalism helps you with further culture gain, Monarchy helps curb unhappiness & Landed Elite helps your capital grow even further. Adopting all policies means free aqueducts and overall better growth for your cities.
Liberty: In the opposite sense, Liberty is based around building wide. Unlike the generally great policies of Tradition, I think there are two you want to go to immediately in Collective Rule and Republic. These may be in different orders depending on what DLCs you have, but the free settler is HUGE in the early game from Collective Rule. Republic allows your newly founded cities to get off the ground quickly. After those two, Citizenship helps with the free worker, Meritocracy helps curb unhappiness through roads & harbours, and representation gives you a very nice golden age and an easier time with future policies. Adopting all policies gives you a free great person, which I would usually recommend to be a scientist, so you can construct an academy.
There are still Piety and Honor to address, though.
Honor: Some Civs want to start war ASAP. Some Civs benefit very specifically from fighting Barbarians. If you are playing a Civ that fits one of these two categories, Honor is often your best bet. Though even War civs I would say, a lot should probably still go with Liberty. You don't even need to necessarily fill out the entire tree, just adopt the first bit of Honor for the Barbarian bonus and you can move onto Liberty. Or in the opposite sense, maybe only Collective Rule/Republic and then Honor afterward.
Piety: Some Civs gain a very specific advantage due to their religion. I'd like to say this is probably the rarest starting policy, but if you are having a particularly tough time coming up with faith in the early game, here is your policy tree. Though in general, most Civs will have this as their second tree, if they even address it at all. Reformation beliefs can be quite powerful, but some of the other policies in this tree are quite lackluster to begin a game.