Nobody knows when the mempool will be less congested. Better do not deposit bitcoin for now on betting sites, you need to also consider how high the withdrawal fee can be on custodial platforms. There are altcoins that you can use instead for now.
You make payment or bet in Casino platform, the thing is that since we are experiencing high fees in bitcoin that doesn't mean that we most withdraw with bitcoin, some altcoins has low withdrawing fees that's more better than bitcoin which you can withdraw with, I could remember during the time my rank was member and I participated in betnomi signatures campaign and fee to withdraw our was high in bitcoin and switch to litecoin and fee was lower than bitcoin fees and I was alright, cool with it, except in such Casino platform its only one option is given and the option is bitcoin and its compulsory that you most withdraw with bitcoin then I will advice people to hold done until high fees reduces.