Is gambling OK? Don't bet it! There's not an easy or instantly obvious proof text answer to that question.
Yes it is 100%, and it is a very bad sin, and if you are into it you should stop and get out of this game, below are some Noble Verses from the Noble Quran:
"They ask thee concerning wine and gambling. Say: "In them is great sin, and some profit, for men; but the sin is greater than the profit." They ask thee how much they are to spend; Say: "What is beyond your needs." Thus doth God Make clear to you His Signs: In order that ye may consider- (The Noble Quran, 2:219)"
"O ye who believe! Intoxicants and gambling, (dedication of) stones, and (divination by) arrows, are an abomination,- of Satan's handwork: eschew such (abomination), that ye may prosper. Satan's plan is (but) to excite enmity and hatred between you, with intoxicants and gambling, and hinder you from the remembrance of God, and from prayer: will ye not then abstain? (The Noble Quran, 5:90-91)"