If someone which follows the set of rules and be discipline enoff. Can people make 50-100 $ a day just gambling in online casino.....?
Anything is possible...so yes, it can.But statistically...the chances, that it won't is probably much much bigger and probable.
Your so right it is possible if you are really really lucky but in statistically the chances to make $50-100 a day in gambling is impossible. You would go negative if you still play everyday even if you spend $20 a day and trying to win. I would prefer on investing than gambling every week you spend $100 in a 5 days you can invest than and double or triple your money. So in your question even you can discipline your self you would still go negative.
If you go in dice game or slots game i am sure you can not make that amount of profit but in sports betting i think you have more chance to make that daily..