I would work on your fundamentals as much as you can before your class starts. Otherwise you're going to drag the class down (you'll be behind your peers, unless Veritas
groups students by ability, like Princeton Review
does), or just not get as much out of it.
I would get some good verbal and math workbooks, either the OG ones or Princeton Review
ones, or even both if you need the extra practice. The PR ones have strategy as well, but I don't know about the OG ones. I don't think so.
3 months is doable if you're really diligent! Good luck!!