Two biggest things: Advertising and allowing U.S. players.
As far as bonuses, I'd do random small gimmick rewards like:
Have a magical hand generated every so often. Maybe it's T
3
for the "magical" day. Then, when someone is dealt that hand, have a bonus pop up that says, "Congratulations! You just got the magical hand. A bonus of $20 has just been deposited in your account."
Then, another day, have a magical hour, where if someone simply opens their account during that hour, they are told, "Congratulations, you just opened your account during magic hour. Open one of the three magical doors to receive your prize." Then they would be given three doors, with small prizes behind each--like $10, $25, and $75.
Casual players love stuff like this. It also gives them incentive to play and login to their account as frequently as possible.