It is sin for me, but not for you. According to everyone, the situation is different. For a person who is generally religious, gambling is a sin, for example I can say sin according to my desire.
For example, there are some religious days in our country and it is a great sin to play gambling these days. He also encourages a bigger sin if he plays in regular casinos.
Were in the same page mate, I also do believed that gambling is a sin too. it maybe true that the gambling is not in the Bible but there is also no gambling place in heaven only here on earth we had it. But I respect the opinion of others here if gambling for them was not a sin.