Without more specifics of 1) what level your learning has been at and 2) at what point your undergraduate career at university will pick up, it is, imho, impossible to give any firm recommendations. Nug's answer is most appropriate (as well as pretty obvious): you should evaluate both the physics and the mathematics courses which a student majoring in Physics at your selected University will have taken (computer science, possibly, also), find out which books were most recently required texts for that course, and work through them. Now, that's a heck of a lot of work! As an alternative, consider a hybrid approach. It should be noted that CC courses are (just like Uni courses) highly variable in quality and thoroughness. One typical, even stereotypical, fault in CCs is the lack of drill with most topics. That is, the student is "exposed to" a subject but isn't given enough problems and time to master it. So, if you haven't done all the problems in the textbooks you already have, that would be my 1st recommendation. Possibly you could merge both approaches. I don't understand why, if you haven't had a course on QM, and hence will be required to take it at Uni, why you feel the need to 'get ahead'. Chances are, getting the basics (the math and classical physics) solid is your best way to prepare. I do agree with the proposition that having an extra (good) textbook while taking a course is a great way to master the material in a course. (but that's one major reason why schools have libraries)... One problem with QM, is that there are a variety of paths through the woods, and Griffiths may not be a good one for the course you will be required to take. Get the Uni course's book 1st, is my other recommendation. And finally don't ignore recent on-line material (course syllabuses, problem sets, video lectures) from those courses which the Uni student would have taken to get to the point you'll be at upon entry.
