Search on ebay for a Traxxas Electric Rustler or Traxxas electric bandit. They are cheap, entry leval buggies that wont get you laughed at when you take it to the local track (they are slower, but they are still "hobby class"). Plus those two vehicles are tough as nails and with your low budget you shouldnt have a problem keeping up with the maintenance.
Here's the most basic Rustler brand new:
http://www2.towerhobbies.com/cgi-bin...=LXJE53**&P=ML
Here's the most basic Bandit brand new:
http://www2.towerhobbies.com/cgi-bin...=LXJE54**&P=ML
Used you could easily get more than what those come with (a battery or two, spare tires, etc etc) for 100 bucks or less....but its still ebay. But follow the advice listen above and you shouldnt have too many problems. Although honestly I dont trust people in general so I dont use ebay.
Also, ask your parents if they will help you make the deal so you can use PayPal so if they cheat you you can get your money back. Just give you're money to them when you're ready to buy whatever it is, and then they can use paypal to purchase your truck!
Ok now about RCs!
-Onroad cars are very resistricted and unless you have an RC onroad track or club nearby, the parking lot can get boring after a while.
-Electrics are cheaper from the start, but they take alot of money to get competitive. They are more idiot proof and are less hassle, but if you want to race you will have to toss out some cash. An RTR nitro vehicle usually will have a fast enough engine to keep you up with everyone else in the pack.
-Stadium trucks are probably the cheapest, but most versatile vehicles. They can go onroad and offroad VERY easily and without many mods. They are what most beginners like to start with because of their toughness and ease to drive.
-Monster trucks are a huge money pit compared to most other vehicles (although the Savage isnt as bad as the Maxxes). They are cool looking but they cost the most the maintain.
-1/8 Buggies are probably the most expensive of all types of RC, and are probably the most geared for racing.
I say get an electric Stadium Truck. For a beginner, that will be the most lasting fun, least hassle, and less costly of any other class you could get into.