As some people have said in this thread, be careful about transferring coins from a gambling site to a US exchange. Most of them contract Chainalysis to spot transactions from known illegal (in the US) sites and addresses.

As a matter of a fact I know someone who had their Coinbase account banned because they transferred BTC from an online poker site to Coinbase, even using a tumbler.

That being said, gambling and illegal coins notwithstanding, I would recommend either Coinbase or Gemini (both are FDIC-insured).