the thing is, over the course of time the car itself is probably not the biggest cost. you will spend lots of money on tyres, repairs, mods, entry fees etc. So if you plan to be doing this for a while I would advise save a bit more money and buy a better car. sure an R31 or whatever is do-able, but you will out grow it fairly quickly. far better to spend the money on a car that is easily upgradable as your skill improves. I would look at a basic SR20 powered silvia. in fairly standard condition they are still driftable and as you get better you can improve the car to match your improving skill and the car can be improved enough to be competetive at a very high level.
basic S13 with a 2 way LSD, coil-overs, and some light engine mods will make a great base. you will thank yourself for it later.