I've been thinking about interactive gambling system for viewers. I'd think it would keep people watching more constantly, and also for Sub Sundays could be special day for these bets. Below few types of bets:
-Will bonus come on next 10/25/50/100 spins; with different payouts
-After 100 spins balance will be -2000€/-1000€/+1000€/+2000€
-Bonus will pay below 10x/50x over 50x/100x/200x (in Sub Sundays special bets, like over 1000x with insane payouts.)
-Amount of bonuses in next 100 spins 0/1/2/3/4/5/below 5/ over 5
-Which symbol will come in next bonus (BoD, BoR type of games)
-And all these type of things
I'd prefer to get some Twitch overlay application, that would keep all the !bet and !gamble spam away from chat, I think the casino adds are enough for it. I'm not sure though if there is any apps that would support it, but atleast streamer "ONSCREEN" have been doing this type of bets trough sliver website. I believe you could find someone that could do app for you, if it seems there is not already good app for it. Also there is the "click the screen"-app that could be usable for bets.
For last, i'm not sure if its possible, but do it so, that the !bet and !gamble and !points command will only show for chatter who writed it. Then the bot tells everyone if someone wins big, and the !leaderboard command.