if a person gamble just for fun like spending few hours and with 20 dollars a week or monthly, i consider it as a normal, ....
Well that is not normal because we don't have the same financial status.
For people who are making like millions in a month basis, $20 does not anymore give them a thrill and it's just a waste of time.
What is necessary is not the specific amount, it's you gamble what you can afford to lose, and that you'll stay consistent following that.