few questions.... Will you be using it on the road all the time? how much driving do you do? How much are you willing to spend? dont forget insurance

personally id stay well clear of a 318is had one before only good for cruising, didnt really like it at all, you really have to go 100% to do anything with it which is ok on track but youll wont do feck all on the road except round abouts unless your used of drifting... got a lsd for it and it was crappy enough aswell and you dont really want to end up welding the diff on a road car.
id say ideally a sr s13, even a ca or a carlton or maybe a bmw with a bit more power (im not the one to ask 318 is the only bmw ive owned)