Welcome to the forum.
Doubleup is an interesting game for a casino, that is certain, and I would be willing to give you a try.
Though, I don't personally feel comfortable enough with directly connectingy wallet to a casino, I would rather just to carry out an on-chain transaction using Bitcoin in order to deposit. Some people will also feel paranoid when comes to connecting their wallet to any service.
And this is completely understandable. We currently don't offer BTC as a currency to be used on our platform, but are working towards allowing you all to do so. That being said, on DoubleUp the players always have full custody over their funds. We just need you to connect your wallet of choice in order to carry out the on chain transactions.
Happy to chat further on this if you have any questions!