After researching about all about bitcoin, now I am thinking that gambling is not good as with that you earn money only when you make someone lose his money when you harm someone, so it is not better to do gambling.
Not really. Gambling is pure luck and has nothing to do with "if he wins, then I'll lose" or "If I win, he'll lose". It's not like a ponzi scheme where everyone robs each other basically and eventually collapses.
I don't think that gambling is wrong, because you can choose whether to do it or not. It's not forced upon you.