I am not sure why everyone only speaks about bounty managers and not about other marketing person. There are a lots of forums and website which are good for marketing like insta, fb, youtube, tiktok which are good for marketing as well.. But no-one is mentioning that.
Most likely this happens because that is the more obvious option as we are in this forum and we know of the existence of signature campaigns, however you are right there are many ways to promote a casino and social media websites are key as casinos can reach millions of gamblers with a single post for free, which is something almost impossible to do with any other media.
Another good option is to try to hire celebrities for your casino, since people love celebrities, a casino that can hire someone that is easily recognizable will gain a lot of clients just because of that business relationship.