I got the nice super flexible silicon wiring through Amazon. Really nice stuff, really a not so nice price. But hey! You only live once (or twice with this new adventure we're creating here). I used 10 gauge on both the cooler and the front by the galley where there may be some higher wattage 12v appliances. For the rest of the 12v cigarette outlets, I used 12 gauge. For the Fantastic Vent Fan, I used 14 gauge wire. For the USB outlets, I used mostly 14 gauge 'cause I had plenty of it-16 wold have been fine by me, though. And for the lights, I used 16 gauge. I know it was overkill, but it made me happy. Also, if I decide to wire more stuff in anywhere, I won't have to replace the wiring because it's not stout enough.
Get the heatshrink butt connectors and the spade connectors. They were fun to work with. And it's nice to be able to connect and disconnect things easily. Which is good for me as I change my mind as often as the wind changes direction.
I have all the little stuff running through a six gang switch. It has 30 amp breakers, which are useless, so I've run inline fuses out of it. I've all the 12 volt outlets but the fridge on one six blade fuse panel.
Have a one or two spare circuits pre-wired. I have one by the galley and a 12 gauge one run to the back. I've never owned a boat where we didn't eventually need one or two. Nor do I expect this vehicle to escape that necessity.
If you're gonna be using more than little stuff on your 12v outlets, get the ones that you wire yourself and use a smaller gauge wire. Remember, "Smaller gauge" means "larger wire".
Get good hardware. Marine hardware is generally manufactured to withstand more severe environments. Don't buy cheap shit. This will be your home. Do you want your home's electrical system wired with crap?
You may want to look at the thread on the top of Electrical section of this forum. You'll find a lot more info there.
Have Fun! I know I did. I turned a simple little electrical set up into a huge project. Who needs 10 USB and 7 12v outlets? Well, I do!
Ted