Reading on RCUniverse is a great place to learn about this hobby. As for "gas", it's a specialized fuel you need to get from your local hobby shop. As for your first vehicle, see what your local hobby shops sell and have parts for. This will help make quick repairs. Some good vehicles to consider are the traxxas nitro rustler, traxxas nitro stampede, associated rc10gt, duratrax nitro evader, hpi nitro rush, xtm xcellerator....

Some may be a little out of your budget, but check them all out to see if you should spend the extra or hold off until you have the extra funds (or if the least expensive ones meet your needs).