For the sake of fun its okay to start with anything below 0.001 BTC just to avoid losing more money
and for gamblers playing for profit i think a fair amont to start with is 0.001 as this stake increase depending on strategy and limit set.
I agree, for now I only gamble for fun and entertainment and don't really aim to profit from it. I realized that gambling can never be for profit no matter what you do, unless you are joining those easy to win promotions the casinos have which can give you small profits.
It doesn't really matter whether who benefits as long as you're having fun. And you don't really need to put in a lot of money to risk. I bet in just a couple of satoshis that i left extra from transfers from trading platform to another. It's usually the game and not the amount that interests me.