Is gambling OK? Don't bet it! There's not an easy or instantly obvious proof text answer to that question.
Nope. It is depend on the the person on how he play gambling because if gambling is having a negative effect on a person and making him like addicted to it and being greedy that comes the gambling a sin if you didn't control yourself and abuse it.
Yeah, the reason we think gambling is a sin because the number of those addicted gamblers are more than successful gamblers. When gambler has no control on himself and lose our money in gambling then sure he will use something bad words for gambling, then gambling is a sin for him and nothing else. But on the other hand, normal gambler or successful gambler not accept gambling is a sin, because they are earn from it.