I'd suggest getting a straight mattress and metal frame, and not spending the money on a headboard or baseboard. We got a full size bed for our son about six months ago from Mattress Firm. It costed around $600, though we made sure to get the water resistant weave (which shouldn't be as necessary for you unless you drink a lot in bed).
We went to Mattress Firm, which specializes in just the mattress, box spring, and frame. They'll also have the same set-up available at most furniture stores. Just pick three around town to check out their prices and test the beds on display. Make sure to talk with an associate while you're there. They almost always seem to have sales on the mattress and box springs if you buy both.
The frame should cost about $50-60. The mattress and box springs will cost about the same each in the $100-$500 range (the $100 will be a foam mattress which you don't want). If you are broke and need something cheap, then you can just get the mattress and lay it on the floor. You'll probably also have a $50 delivery fee you'll want to figure in while comparing prices. At furniture stores, you can typically get the delivery fee waived if you buy a certain dollar value of furniture. So if you're planning on getting a couch and some other things here in the first semester, shopping for all of that at once can save you on delivery fees.