When I was a poor college student I had one bike for everything - transportation, recreation, fitness and touring. I'd suggest you look at bikes that will accept a rear rack (i.e., no carbon seat stays unless they specifically have rack bosses) and might have a more comfort-oriented geometry than a full-on race bike. Not going too expensive is actually a bonus on a transportation bike, since it'll be less attractive to thieves.

But yeah - try out different bikes, see what you like, what fits, what speaks to you. Good luck and enjoy the search (and welcome to TE)!