Although i think the most common would be the Muslim religion, i don't think they are supposed to gamble but i may be wrong.
I do not think religion has anything to do with gambling. Even if your religion tells you it is wrong, you will still gamble if you want it. I think the more you say that gambling is wrong, the more people will gamble. Because it is exciting to do something illegal and get away with it.
I strongly agree with you , gambling is just for entertainment only but it still involves money on it. Gambling would be bad if you get addicted into it and you lose all your money and it would definitely wreck your life. Dont treat gambling as a source of income because it would lose your money right away.