pokersheperd,
I am not familiar with your site, but if you do not have your site optimized very highly for any keywords, I would spend a few bucks on an seobook. I know Randy has one that he always recommends.
As webber said, spend some money on buying some links from very relevant quality sites. There are plenty of webmasters selling some space, and I imagine this will take up a majority of your $500 budget.
Maybe take $100 of that and pay someone to write some quality articles and reviews for you, unless you want to do that yourself.
Good luck.