They should set their limits beforehand. For me, they should never spend the equivalent of their salary in just one bet. You should only bet with your extra money not your entire paycheck of the month. Because if you lose, what will your plan be then? Some only takes 1%-2% of their salary but it depends on how big the salary is
No matter how big or small the salary is, if you want to decide that you will spend 1% of your salary on gambling, you should keep to the rules. The amount to spend from your salary should not vary, especially on the increase side. If the 1% is small, instead of increasing the amount, it should be decreased if the money is too big. Sticking to a budget in gambling helps in controlling one’s gambling behavior.