If you think that person has a great potential as gambler and can profit with it, just do it.
He will probabily not mind in at least trying.
but always remind him that playing gambling game can attract him to become addicting in gambling and he should know about this so he can prevent to become the addicted person in gambling. besides that, you must tell him that he needs to make a limit on the money that he wants to use so he can avoid getting a big loss of the money. this is hard especially if he always attract to the game and want to play more the game and he can become the addicting person.