The fact that you win 9% on each round isn't fair at all, most casinos have a house edge between 3% and 1%, but 9% is just too greedy.
If a user sends less than 0.02 ETH, he will get the message 'Not enough ETH!', but he doesn't get his money back, and I don't like those games where small mistakes make you lose money.
And there is not clear at all what happens if I send 0.03ETH, would I get 1.5 tickets or 0.01ETH would be lost if I send that amount?
don't worry, this kind of business plan won't work or survive. some may try at the beginning. but the longevity of this project is questionable. also, the way this project is presented is you have the notion that this can disappear anytime. maybe once collected enough money for the owner. who knows? maybe the OP needs to try harder on delivering his gaming platform and earn at a lil bit of trust from his potential users.
It's a smart contract and all things are clear. why are you talking about trusting when code is processed by a machine!?