You wouldn't expect a "trawler trash guy" to have much to say about a galley. Oh well.
Sinks are an easy place to start. If you live on a boat, you must do dishes. Most boats under 50' do not have room for a dishwasher in them. So... You gotta wash dishes. My preference is to have two good sized sinks so that I can wash dishes in one sink, and rinse them in another. This is my preference. Some prefer one larger sink.
Be aware of sink depth. A big sink is really nice to be able to wash bigger pots, pans, and bowls. But if that big sink is really deep, and especially if you're on the tall side, then your back may eventually complain that you're always stooping over when doing the dishes.
These are just things to be aware of. Though the reality is that most "trawler trash guys" aren't going to prioritize boat choices based on the galley setup.
Most 40-ish foot boats will come with an oven and two or three burner stove combination. Sometimes this will be an electric unit, sometimes it will be a gas unit - typically propane.
A propane stove could be considered a must if you plan to spend a lot of time cooking while anchored out. This is because an electric stove draws an enormous amount of power. While you can get away using a microwave (at about the same power level as a stove top) or just a few minutes, the stove top will need to be on for a much longer time. This will quickly drain all but the largest battery banks, and essentially require that either shore power be used, or that you fire up the generator any time you want to cook when anchored.
The disadvantages of a propane stove (efficiency considerations aside) include (obviously) that you must periodically refill the propane tank, and that you have to be mindful of the safety considerations of operating propane appliances. While propane can be expensive and hard to get in remote locations, most of my friends reported that a 20 pound propane tank would last a very long time when only used for cooking.
My trawler came with an electric oven and 3 burner stove top. That worked for me, because I understand electricity, and didn't want to have to worry about the potential issues of propane plumbing, solenoids, refilling tanks, space for a propane tank, etc. I also wasn't thinking about how hard it might be to cook on the hook. I figured I'd have a grill and a microwave. What more does a guy need? Hm.
Eventually, as I spent more and more time living aboard, and thus cooking aboard, I had to face the reality that my 40 year old stove top just wasn't working reliably. I tried getting a two burner portable electric cooktop. That worked, but also suffered from quality issues. It was nearly impossible to accurately control temperature on a cheap two burner cook top.
Finally, I took he plunge and got a two burner induction cook top. Induction cooking is significantly more efficient that traditional electric burners. Induction cook tops are more expensive, but they all have digial controls, which means that your heating should be far more precise and reliable. It takes a little getting used to. And given the choice, I'd still probably prefer to cook with a gas flame that I can see. But if I have to go electric, the induction cook top seems to be a good option.
One of the big down sides of an induction cook top is that you need pots and pans that work with an induction cooker. This means they must have at least one layer of steel in the bottom. The cheap pans you may have accumulated for the boat generally won't work.
Another significant constraint on the boat is storage space.
My girlfriend introduced me to Magma nesting pots. It turns out this is a really great solution to boat pots and pans. It's Magma (same company as the Magma grills) - so they know how to do stainless steel. They're also rather proud of their work. This stuff is not cheap. However, it's good quality, and will hopefully last forever.
The really cool part is that a reasonable set of pots and pans will all nest into a very small storage footprint. This is critical for a boat! The pots have detachable handles, which is a critical part of being able to nest for storage. I realized they were cool when I first saw them. Now I'm coming around to the idea that I'm going to have to take the plunge and make a significant investment in cookware. No one that knew me well would have ever thought I'd spend big bucks on kitchen stuff!
I should probably write a separate section on the boat's plumbing system. But for now, we'll just talk about the water used in the galley.
My boat has a water capacity of approximately 150 gallons. For two, this is enough to last nearly a week, assuming we're taking frequent showers.
Most marinas provide potable water at the boat slip. Many boats have two options for dock settngs. Typically, you use a garden hose to connect to the spigot on the dock, and fill your water tank. The DC water pump in the boat then supplies water to the various faucets. Some boats are set up for a direct hose connection to shore water. In these cases, the hose connects directly to the boat, bypassing the water pump on the boat. The water pressure of the dock supplied water supplies the pressure for your plumbing.
CAUTION!!! IF you use a direct shore water connection, ALWAYS attach your own water pressure regulater, and NEVER leave the boat with the dock spigot turned on!!! Just like shore power electricity, the water pressure supplied from the dock might be low, and it might be high. If you happen to be the only one using it, a high pressure surge might blow out fittings or lose plumbing connections.
If a catastrophic leak in your plumbing system occurs when you're using a DC water pump and water tank, the worst that happens is that you empty your water tank into the bilge, and then the bilge pump gets to pump the water overboard. If you have a shore water connection and experience a plumbing failure while gone, or asleep, nothing stops the flow of water. Your bilge pump may eventually die (either through wear or dead battery), and you can potentially sink the boat. This has happened. I've used a shore connection before. But after blowing out a swim platform shower wand, I decided it was far better to just use the water tank and onboard water pump. Yes, I'll probably eventually wear out my water pump. But I won't flood the boat.
So... on to water quality.
When you buy your boat, you may not want to assume the water tank is clean. If possible, flush it - several times. Go online and find the calculation for how much chlorine to add to your water tank to "shock" it and kill anything that might be in the tank. Flush the tank several times before you even consider drinking the water.
When I fill my water tank, I attach a RV water filter to the hose. This is a "Recreational Vehicle" filter, not a "Reverse Osmosis" filter. These are generally sediment based, activated charcoal filters, maybe 20 microns. This type of filter ASSUMES that the water is DRINKABLE. This filter is just for improving the taste of the water and possibly removing occasional big chunks of dirt that might get into the line... Run the hose for several minutes before you start filling your tank. The RV water filters can be bought at Walmart or on Amazon for about $10 each, and should be replaced about once a month.
On my current boat, we also installed an internal water filter between the water tank and the pressurized water pump. This is a simple fixture that holds a 5 micron filter cartridge. The cannister holding the cartridge unscrews to allow periodic replacement of the filter.
In addition to the water filters, we use a Brita pitcher to further filter water used for drinking, cooking, and in the tabletop icemaker (see below). Some might think this is overkill.
If you're truly going to do a LOT of cruising in remote islands, a watermaker is the only practical way to go. But that's a whole different discussion. And my cruising hasn't gotten to that level yet.
In reality, if you're not going to do a lot of cruising in remote locations, a water maker doesn't make sense to have. They are very expensive to set up, require regular maintenance, take a LOT of electric power to operate, and should not be used in a marina environment or anywhere that the water is very dirty. They're great if you're in a clear cove. But if you're in extremely muddy, brackish, or poluted water, don't use your watermaker. I have also been told that they don't work in fresh water.
You may laugh, but an ice maker is actually a REALLY nice thing to have on a boat!
Many 40'ish foot boats came with icemakers. The standard by far is the Uline built in icemaker. These run between $900 and $1100. In MOST used boats, these no longer work. In some boats you might be lucky enough that they may cool, just not make ice cubes. In that case, you can use the ice maker to keep the vodka cold, or as back up freezer space.
Replacing the Uline unit when it fails is EXPENSIVE. You can buy a hell of a lot of bags of ice for $900! But then you have to go get the ice. And you have to have a cooler for the ice, and a place to keep the cooler. And the ice melts as soon as you've gotten it...
An ice maker is a really nice thing to have. Especially if you like ice water or mixed drinks.
A less expensive option than the Uline build in icemaker is a tabletop icemaker. There are several different brands of these, and they run about $100 on Amazon or at Walmart. They are very simple. They run on 110V. You plug them in, pour water in, and they make ice. The nice thing is that you can use bottled water, so that you know you always have clean ice (if your water tank situation is "iffy").
The tabletop icemakers are smaller than that Uline built in models. They also make less ice. They work ok for one or two people. For a party, you will need to plan on a cooler and a bag or two of ice.
Tabletop icemakers do not keep the ice cold. As soon as the ice is made, it starts melting. The melted ice runs back into the water reservoir, where it is made into new ice. Unfortunately, the ice that is made is "wet ice". The cubes are smaller than those made in ice trays and in the Uline icemakers. That's not a big deal, and some people prefer the smaller cubes. But they melt faster. And because the icemaker doesn't have a freezer section built into it, the ice sticks together fairly quickly. If you want to save up ice for a group, it's fine to dump the ice into ziplock baggies and throw the baggies into your freezer. But because it's "wet ice", the cubes will freeze together fairly quickly. If you're not careful, you'll quickly end up with one large mass of ice. Best case, you'll need to plan on slamming your bag of ice cubes on a counter or floor to break up the cubes before you'll be able to use them.