I would add one more important thing, which is that you should not gamble with money for which you do not have a valid proof of origin - because I recently read a case where a user won almost
$4 million with a deposit of $100k, and now the casino refuses to pay him win because he still hasn't been able to show them where the money he gambled with came from.
This is a funny to me. The casino allowed such huge bet and after the winning they realized the source of the money should be investigated? This is unfortunate and that means the casino is trying to be funny. They are asking to know the net worth of the player or what...
So I would play in a reputable casino where I know they would do all the background check they need to do and would release my winning incase I get lucky to win.
Source of income is like the document that is request for when a gambler wants to pass a level 4 kyc verification on Stake.com, so yeah, proving source of funds to casinos is nothing new, the only problem there is that, even before the casino allows a player deposit such a huge amount of money, the casinos should have asked the gambler or user to pass all level verification which includes proofing the source through which all the fund the gambler will be using to gamble in the casino comes from.
What they are doing right now is trying to cheat the player, but such a matter can't be handled carelessly, the user should stand his ground, and if he has the capability, he should seek legal help, this is if the casinos hasn't paid him already.
My most important practice to staying safe in gambling is to gamble responsibly, and this is, adhering to every responsible gambling tips out there.