I'd suppose I'd focus on the basics of what you use based on your own level of handiness. that might be just a screwdriver or two for some folks....
I've always carried my basic tool bag from home. I'm fairly well handy and I have a few big tool boxes and lots of odd things on the shelf, power tools, etc...
but for about as long as I can remember I've maintained a little tool bag...maybe something like 10in x 12in in footprint, 6 or 8 inches deep...with little pockets all around. A couple sizes of each type of screwdriver, standard pliers, linesman pliers, maybe a channel lock, needle nose pliers, a small set of "tiny" screwdrivers...a few commonly used nut driver sizes, a box cutter knife, maybe a scraper or small putty knife, measuring tape...those kinds of things
and a multi-meter.
oh, I also typically carry a cordless drill/driver and a small selection of bits and drivers for it.
I've used just about all of it...a lot early on when I was working through all the stuff the factory forgot to do...like put that second screw in all the drawer slides for example.
I've still had to stop at a hardware along the way and buy a little thing or too I didn't have handy, especially bad when I know I have one at home, but it is what it is...you can't bring everything.
I don't bother with larger stuff to work on the chassis.
Not too long ago, i put together a duplicate kit to just leave in the RV. Some of those tools I just bout some rather cheapy stuff but the same sorts of things...and I added a low cost IR tempertaure "gun" and a small selection of misc. screws and such