The address from a gambling website will be always different because they use bitcoin API-s like Bitpay. It generates a new address every time they send you bitcoins. Same when you deposit there, they always give you a new unique address. Main address of the sender is the one that sends you bitcoin, click on bitcoin transaction to find it on blockchain website.
I've clicked bitcoin transactions in blockchain but I could not find the original sender's address, how so I can find it, whether it be learned? where i can get guidance on this?