You no longer get XP for using skills. Instead you get skill increases which may be spent at a menu as loot, rare drops from killing enemies, and as quest rewards. You will find various "insight potions" that give you points toward leveling up. Each insight potion grants 30 points. You can utilize these potions using the "Increase Skills" lesser power. This is to encourage the player to actually go do things; no matter what you do in the increase-by-usage system, it is always better to grind skills in dumb and tedious ways.
The cost to increase a skill level depends on your current skill level. With default settings, the amount of points required is equal to your current skill level. For example, if your current skill level is 5, then it will cost 5 points to increase that skill.
The MCM has an option for Progressive Skill Costs. Enabling this makes insights follow a different cost curve; generally it lowers the cost below skill level 50, and increases the cost above skill level 50. Overall this will extend the time required to get to peak power, as skills cost much more when they reach 80 and above with this setting.
There is also a multiplier in the MCM menu for skill costs. For example, setting it to 1.1 will make skills require 10% more insights to increase.
Insight potions (greater) gives greater skill points when used
Greater skill points are required to advance skills past a certain level. (Configurable in MCM, default is 50)
Greater skill points can be used as a substitute for regular skill points. (Configurable in MCM, default is yes)
Insight potions (greater) are found exclusively in more difficult content: roughly a 50/50 split between greater and regular insights in mid-level content (e.g. Falmer, giants) and high-level content (dragons, dragon priests) has 100% greater insights
Regular skill points can be converted to greater skill points. (Configurable in MCM: default is disabled, options for conversion rate are 5:1 and 10:1)
The requirement for greater skill points can be disabled entirely in the MCM. Greater insight potions will still spawn but will function identically to regular ones
Insight potions give 30 skill points each when used.
Diluted insight potions (and greater diluted insight potions) have a high chance of being found on various types of enemies. These potions provide 3 instead of 30 skill points, and will be generally found on every enemy in an area.
Diluted insights are dropped by enemies at a rate of 80% per "category" the enemy falls into. Examples of "categories" include where they are located and what faction they belong to. So enemies in the "bandit" faction will have an 80% chance of dropping a diluted potion of insight (regular), enemies in any location with the "cave" keyword will have an 80% chance of dropping a dilute potion of insight (regular), and for example, a bandit in a location with the "cave" keyword will have 2 rolls of 80% chance at the insight potion aforementioned. Some enemies will stack several of these chances, some will only have 1.
You may rarely find regular insights/greater insights on enemies. Some particularly high-level enemies have guaranteed drops of regular insights.
The leveling curve is now different, requiring twice as much XP to level from level one, but a bit less towards the later levels.
Each day spent in jail now makes you lose 10 normal and 10 greater insight points (which can cause them to go negative).
Jail is capped to 7 days maximum, each day spent lowers bounty by 1000 gold.
Murders are lowered to 5000 gold bounty.
Training is still possible but limited to 1 per level.
Changed journeyman/expert/master skill levels to 25/50/75. Master tutors won't teach beyond skill level 75, expert beyond level 50, etc.
Training from trainers has a higher base cost and also scales with your level smoothly.
It is highly recommended to use the Simple Training Overhaul mod, as it makes training much more useful by changing it to fortify skills rather than increase their base value.
Derived Attributes Changes
This is currently being tested as a separate plugin before being fully integrated into 3Tweaks. If you would like to test it, you can download it here.
Levelling up increases the attributes by different amounts.
Health increases by 5 when chosen. Also grants bonus disease and poison resistance.
Stamina increases by 7 when chosen. Also grants bonus stamina regeneration and carry weight.
Magicka increases by 7 when chosen. Also grants bonus magicka regeneration and cast speed.
You also get a choice of a secondary attribute to increase based on what primary attribute you chose.
Health: incoming damage reduction, bonus melee damage, or shout cooldown
Stamina: attack speed, archery damage, or movement speed.
Magicka: magic resistance, spell cost reduction, or spell power.
There are no breakpoints, so choosing an attribute will always give you an immediate bonus, without having to worry about "catching up" to benefit.