When it comes to on chain gambling, site's names that comes to my mind is directbet with its sports betting and luckybit with its plinko game.
I believe On Chain gambling is history now.
I still missed that sports betting site named directbet. That was the easiest and most trusted sports betting site i had ever seen. I wonder why after its departure, no one courage to make the betting site on a similar code.
I think they have another project that they want to focus on and they can make a similar code but the problem is most of the blockchain are experiencing high transactions and it will congest the network and people will be pissed about it if their bets doesnt get graded instantly.