Originally Posted by SirKarnage

Nitro refers to Nitromethane fuel.
Gas is well... gas, generally mixed with oil, like a weedeater/2 stroke engine

As for what you should get, well thats totally up to you. like the previous poster added.. there are kits(you assemble), pre-assembled(no engine/eletronics), and RTR(ready to run-only feild equip needed) versions of almost every brand and style you could imagine.
It depends on what you want to do, how much space you have and the type of surface your going to run on.
the large scale (1/5) like the 5B takes alot of space run in.
the 1/8 off road buggies /truggy vehicles are "generally" geared more for racing.
Monster trucks- though are raced more and more, are generally the back yard basher vehicles.
1/10 scale trucks - 2wd mainly, are cheaper, yet take more control to drive in most cases. yet still offer tons of fun.

As for a brand.. thats up to you. the smart thing to do is figure out how your going to buy parts. Local or on-line. if your sticking to your local shop, go with a GOOD brand that they stock parts for or are willing to order when YOU need them. If your going on-line for parts then just pick up what YOU think you would like. Check the major outlets for parts stock, Amain, Tower, Horizon, and countless others to name a few.
There are alot of people that will say one brand over the other due to their personal preference.