When gambling you will always win some and lose some no matter what...but bear this in mind,70% of all gamblers get ahead,90% of them give it all back

This goes for the average gambler...only 10% ever really cash out any significant profit.First learn how not to be part of the 90% that give it all back,and most of the time their initial bankrolls hehe.Set a goal and cash out your winnings but keep your initial bankroll for later.
I can tell you how to make money most of the time,but sometimes you will lose...If you have 50$ then you should aim at playing blackjack for like 2$ a bet and use the martingale if you plan on quitting really early that is.
This is what I usually bet when playing blackjack and it works most of the time,if I have 50$ I won't chase a bet higher than 6$ so I bet 2$ if I lose bet 4 then 6 for example and quit if I lose all 3 and start over.Flat betting is not better or worse in a long run basis,but short term the martingale seems to be ok.
Anyways if you get ahead and reach your goal quit there,if you like slots well take 5$ of your winnings and play slots 25cents a spin,also your goal should be relative to your bankroll and how much you are betting,for example a 50$ bankroll would mean a 20$ goal would be good for one session.