iam use xapo because very easy use
Wait until you will be asked about account verification, they will block your account because you will receive coins from address they will find 'suspicious'.
It might be every gambling site or even faucets with integrated little games like freebitco.in. Then you might evaluate your opinion about them.
If you don't want any problems with your coins in the future (and you need online wallet) switch to blockchain.info.
If you receive or send small amounts of bitcoins maybe you won't need to send verification documents. I'm used this wallet to send or receive funds from or to HYIP's, cloud mining or sports betting but they didn't asked to send them documents. But maybe they choose users by random factor.
With Xapo your every transaction is monitored, your every action noted, but there is no way they would know every gambling address.
There are so many niche, small gambling sites around and HYIP sites are appearing and then vanish over night.
Anything related to gambling is direct violation of their ToS.