Yeah I use facebook, for my gambling stuff. If you want to directly advertise for a casino you'll need at least a budget of 10k a month. Or what I did when I first started out was just give away a free gambling guide, since that did not violate their TOS. Sometimes my ads would get rejected and sometimes they would pass through. It just depends. But I would make sure you have a landing page because you don't want to lose potential customers.

I think you can try adbrite for sure - also there are few new companies for affiliate options - since gambling site is well promoted through an affiliate network

hope this helps...

Have a space for a 160x600 banner, ideally for blackjack related site. Price around $15/month.
My website is geekyfox(dot)com