That's a good idea. I usually toss a few screws when I work on my RC's, or at least deligate them to the junk drawer. I consider them a parishable item. I keep a slew of screws on hand from 2mm up to 6mm in every length I can find. That reminds me, I have a few sizes I need to restock.
I like ball end hex wrenches, but only use them when they make a job easier. The ball ends will wear your screws out over time, and it is much easier to strip a problem screw using them. I rarely use them to break a screw loose, or final tighten a screw. If I have a screw that requires the use...
Man, you can go absolutely crazy getting geared up to work on RC cars. I am a bit of a tool junkie, but I use everything on my RC bench from time to time. Sounds like you got the basics, and you will figure things out as you go.
You might grab some silicone spray to keep the chassis and such...