First, you can go a hell of a long way with 'coat. You won't win 20 points at the Nats (you'll always have seams), but you may be surprised at how well you can do at local contests.
Second, the way to get better at building straight is to build a lot. It'll help with your RC building, too -- a plane with warps compensated by the radio doesn't fly nearly as well as a plane with no warps. For that matter, as long as you get the tail feathers level with the wing you can deal with a warped wing by tweaking the flaps as well as you could with aileron trim.
Third, I suggest you choose a kit and just build it. My suggestion would be a Sig Twister (particularly if you want to kit-bash it into a Fancherized Twister), or just about any profile plane with similar wing construction. If you want to scratch-build and you don't mind not being able to compete in profile, consider Tom Neihbur's "Hobo" -- it'll be almost as easy to build and repair as a profile, and it'll look & fly slightly nicer. (If there's a kit for the Hobo that someone knows about -- speak up!)
(I'm suggesting the Twister because the wing construction makes it easier to fix warps after the fact, and it makes it more survivable in a crash. If you don't expect to crash very often, or if you build quick, go ahead and build a plane with a sheeted leading edge. If you build it carefully on a jig it should be quite warp-free.)