Just need some servos, a battery pack, a radio, and a receiver and your good to go. (dont forget a good air filter and somefuel)
If you are racing your going to want a fast steering servo ( prolly .15 -.13 seconds at 6v) for throttle/brake you'll prolly want something around 60-80oz tourque range. Get you a 1200Mah battery or something close depending on your budget. Finally a decent radio and receiver. M8orM11, XR3orXS3 etc... (Jr, HiTech, AirTronics).
If you are just going to be bashing it, go to your local LHS and buy just about any decent radio setup. It will usually come with a decent radio/receiver, crystals, 2 servos, and a AA battery holder in one box and run under $200.
Oh and while AM is fine, If you have a couple extra $$ go for FM, better range and better signal quality. There is usually not "much" price difference between AM and FM but you didnt specify your price range, so...