PPC is expensive and not available in Overture and Adwords (the 2 places you really need to be to run a successful PPC campaign IMHO). For an effective off-brand PPC site even poker terms are well over a dollar per click, some as high as $30. Unless your conversion is unusually high, I wouldn’t go that route. You may want to play around with it a little bit, but don’t dump the whole $500 into a $30 per click campaign off the bat.
My suggestion is to optimize your site for the search engines and spend the money on high PR site links. For $500, you can buy a linke from a PR8 gambling related site for a few months that will increase your site strength (some call this PR, but that’s misguiding) and that increases your search engine rankings. Make sure you aren’t in the sandbox though, or else you will be wasting your money on links until you are out.