The Bible does not directly mention gambling for money. Neither does it provide an exhaustive list of forbidden behaviors in several areas. That is not the Bible’s purpose. Its purpose is to draw people to God. Anyone who finds himself asking, “Is it okay to…” ought to first question his motives, especially since the Bible says "...whatever is not from faith is sin," (Romans 14:23).
Gambling is leaving to chance what you should trust to our Lord. Christians should trust in the providence of God and not in "chance" to provide for them. This is why gambling cannot be endorsed biblically.
Matthew 6:19-21 says "Do not store up for yourselves treasures on earth, where moth and rust destroy, and where thieves break in and steal. But store up for yourselves treasures in heaven, where moth and rust do not destroy, and where thieves do not break in and steal. For where your treasure is, there your heart will be also.” Why do you want to gamble? To provide for your needs? Jesus continues, saying “seek first his kingdom and his righteousness, and all these things will be given to you as well.” (Matthew 6:33) Gambling can, at times, betray a lack of trust in God, that he will provide. Or is it merely that you want more money for the pursuit of pleasure? Ecclesiastes 5:10 observes that “Whoever loves money never has money enough.” But he who loves God first receives what he truly wishes, joy (Psalm 37:4) which outlasts fleeting pleasures, the treasures which Jesus warned us about storing. In the end, one must ask himself, who am I serving, God or money (Matthew 6:24)? We cannot serve both.
Whoever asks this question must decide for himself if he can have a pure motive for gambling, for spending money on toys, vacations or movies, and even for helping the homeless. Even good actions can have bad motives. The human heart is horribly deceptive (Jeremiah 17:9). Because of this, if we truly face ourselves we must admit that it is difficult for us to do nearly anything purely for the love of God. That is why we need grace. For our attempts to do good always come up short, but God’s grace never does (Romans 3:20-24). Christianity, after all, is not a set of rules, but a love relationship with our grace-giving Father.