This is really difficult to tell and depends on how much you're willing to spend for insurance purposes. The problem is that
cheap student car insurance does not really exist as you're in a age group which insurers consider very risky. However there are things you can do to bring the car insurance quotes down. You can for example get a car which is in a low insurance group to start off with and insure it Third Party Only instead of Fully Comp.
What I think is best for you to do is to type in your details along with the car's in a car insurance comparison site and see what prices you are being quoted. You can play with the voluntary excess and see if that makes any difference. If you see that you can afford the premiums, then go for it, otherwise you'll just have to wait until you're in a better financial position.