In terms of paid traffic for casino, Adwords is king. It takes sometime to optimize especially as you will need to get your quality score very good or you going to battle to compete for the top converting keywords. The only key challenge I see is if you going to do this whitehat, you will need to get the account white listed by Google for casino and they might ask you for copies of the gaming license of the operators you are promoting, and then obviously if you want to be white listed it will have to be in a regulated market, for example UK. When it comes to BH, well thats another ball game. Good Luck