When I was 17/18 I used to drive my mums old Mk2 Astra, 1.2 litre. 5 door. Not cool.
Wasn't till I was 19 that i bought my own car, a Mk1 Astra GTE. Was £880.
What u should get depends on lots of things, but mainly the amount of dosh you have/wana spend I suppose. If your young and new to driving, get something cheap, easy to work on and cheap to insure. At least for a year or so. And try not to crash it.
steve