Well with a bitcoin casino its always going to be tough because you are promoting a niche type of site pretty much. Anyone can promote a regular mainstream casino where all you need is a credit card to play and earn revenue however for bitcoin you need to find only the crypto audience.

You can't just spend a bunch of money advertising on facebook because your audience won't be geared towards crypto. They will visit the site, get confused what "Bitcoin" is and just close the site.

Hence you need to do your research and find the most efficive method. Many people opened up "crypto casino review sites" and try and get them popular. If they get some organic high search engine google listings then they might get traffic and get high quality revenue that way. However even those are saturated these days.