If I am not wrong, more than gambling, its an interactive/skill-based Bitcoin faucet game so microearnings section would be the most appropriate. And as far as advertising like others said, signature campaign, advertising on top Bitcoin ad networks, Coinad/Coinzilla/Cointraffic/Mellowads, paid postings on Bitcoin sites, and even PTC sites. Also adding multiple payment options, direct/through micropayment platforms would be a good option.