I'm a soon-to-be 3L on law review at Pitt.
I bought all new books my first semester, study aids, and everything - total waste of money. I now buy off of Amazon, e-bay bidding, and half.com and spend about 1/3 that of my classmates who still go to the bookstore.
(1) Study Aids: If you go to campus bookstore, they will try to push these on you. I have seen this happen for myself and have pulled 1Ls aside and told them the following:
(a) Hornbooks - Don't buy them. The library has them. The bookstore was particularly bad about pushing the Civil Procedure one on students last year.
(b) Outlines - 2Ls and 3Ls will happily give you their outlines or course notes. The Pitt Law Women's Association (PLWA) stores old outlines online. I used these quite a bit and found them helpful if I had zoned out in class for a few minutes. As for commercial outlines, I would honestly wait. Some people will tell you to wait until October, I would personally wait until you are close to finishing a major component of the course (which could be in September). Some commercial products are far superior to others. Many contain errors. If you want them now for peace-of-mind, I recommend the following:
(1) Legal Process: Glannon's Multiple Choice book and his Examples and Explanations one. These are the ONLY ones I would recommend getting now and may actually even be required for some legal process classes.
(2) Criminal Law: I didn't use a study aid.
(3) Contracts: Professor Madison had recommended the Concepts and Insights series book (it has a blue cover) for my class, which puts contract principles in plain English. I'll probably sell mine in a few days. For outlining/learning, some people (myself included) prefer Emanuel's over Examples of Explanations or Gilberts for contracts.
(4) Torts: Glannon's Examples and Explanations.
(5) Legal Writing: Some sections list a book by Diana Hacker. I bought it, and I've never opened it. I have the new bluebook, but I ordered it from Harvard's site - it came within 3-4 days.