Best advice is to try a few if you can before you buy.
Many people will tell you that the car they drive is the best around, be it AE, Losi, Mugen, Hobao, Kyosho, Xray etc etc but until you actually try one, you'll never really know.
Theres a few new cars on the market, the Durango DNX408 and the JQ THE car to name a couple, but the jury is still out on both models, having only been released in the last month or so.
Another idea is to buy something similar to what a few of your clubmates are running, that way emergency spares should always be available. Also check the price/availability of spares. Kyosho tend to be a little expensive, Mugen a little hard to get hold of etc etc.
Without sounding obvious, dont forget you'll need an engine, servo's, radio gear, wheels/tyres, starter box, glow starter, fuel bottle, tools, spares etc etc. Check the second hand section on here, some nitro stuff comes up occasionally, but you may be better off on MaxBashing as its nitro dedicated and most stuff sold is from reputable racers who tend to look after their gear.
Dont buy from ebay unless you are really sure of what your getting!
Each model has its merits and its pitfalls. Chances are, whatever you buy will be better than you are for a while anyway.
My 2p.......buy a Losi 2.0 or EU. Brilliant, best car ever......but Im bound to say that
