Okay, I still don't see, from just a couple of collections and some SLs, what would give you a 515!!! Did you get your scores from HERE or are you using FAKOs (scores sold at, say, TrueCredit.com)??
Were you late on your SLs? How old are the collections??
Good news for you, though. If you have $2K you can "spend," you can take that $$ and put it on a secured credit card. Bank of America, from what I've been told, is the best. It will unsecure (also known as "graduate") to an UNSECURED PRIME credit card in 9-12 months. And of course, they release your original funds back to you. Some cards even offer to put the funds in a CD account -- which will earn you some nice interest.
Meaning, if you have a 515 NOW, when that card (or you can get two -- get a second with another company) graduates, you'd be looking at least a 100-200 points rise!!