Answer is in my opinion, consider your country's inflation. If inflation is high enough your money is worthless anyways so you are more safe to gamble it without any issues.
In a way, yes, but also it would be better used in an investment rather than in a casino gamble.
And the faster you do it, the better returns.
Tomorrow's value of that money will be way less than what it is today in a high inflation environment.
I guess he has money to spend on his investment but its better to suggest what better figure he should use for his gambling activity since maybe he's confused on what figures is best to used since maybe he want to have proper budgeting on all activities he want to do. Then provably maybe 5%-10% of his income is better to use for this activities since this could not hurt him so bad if he lost that amount but as well he could enjoy the amount he used especially if he is not the type of person who bet all trying to gain fast profit. Just aim to have fun and bet small for sure he can get satisfied with that amount especially if they have good discipline.