So you are basically thinking of forming some "Legit Ponzi" gambling scheme.
Basically exactly like a Ponzi scheme except you know its a scheme and gambling so it might be somehow legal.
Basically 10 people send some BTC and the last person gets nothing after a certain period of time while the first 9 get equally divided up portions.
Is this what you are thinking?
10 people will send BTC but only 3 will be picked as the winners and they'll split the 90% of the total amount the remaining 10% will go to the house.
What OP wants is to make a blockchain based lottery. I'm not against it but it'll be expensive for those who want to bet with a small amount.
You want to put each bet to blockchain? What about transaction fee?
Now it 30000 sat per transaction. It's too much.
That's a bit much. You can add whatever fee you want.
What if the confirmation takes too long ?