I bought everything new, now I've graduated I have an impressive bookshelf - which I never read. So my advice is to get everything cheap, except those you think you'll use as a reference later.
I'd agree with this to an extent.
Look at the reading list/talk to your lecturers and see what is needed most, normally you probably only need one or two books for most degrees that will be your core books, used a lot. Buy those and then just go to the library for the other books.
I only bought 3 books for uni for my undergrad, all used frequently for a variety of modules and years. Also less books mean (at least for me) that you will probably spend more time looking in journals and at papers* which is something that will benefit you in later years of study.

*I take it you are in first year? In which case be very careful what books you buy as they may be way to basic when you hit 3rd/4th year!