To what in you does gambling appeal? Contentment? That seems unlikely. Covetousness, maybe? Greed?
1 Timothy 6:8-10
8 But if we have food and clothing, with these we will be content.
9 But those who desire to be rich fall into temptation, into a snare, into many senseless and harmful desires that plunge people into ruin and destruction.
10 For the love of money is a root of all kinds of evils. It is through this craving that some have wandered away from the faith and pierced themselves with many pangs.
Whose money are you risking in a game of chance? As a Christian, aren't you a steward of the money God has enabled you to obtain? Isn't all that you possess ultimately His? Yes. How are you being a good steward of what God has given you by blowing it on gambling?
The Christian person is to be under Christ's Lordship, under his rule and control. In this circumstance, all that they are and possess is at the disposal of their Lord - especially since it all has ultimately been given to them by their Lord. The strength and intelligence to earn money, the capacity to obtain skills necessary to work gainfully, the provision of employment - all these are from the Lord who imparts them to those under his authority, in particular, to serve his eternal, spiritual purposes, not to be squandered in games of chance.
Colossians 3:1-2
1 Therefore if you have been raised up with Christ, keep seeking the things above, where Christ is, seated at the right hand of God.
2 Set your mind on the things above, not on the things that are on earth.
Matthew 6:19-24
19 “Do not lay up for yourselves treasures on earth, where moth and rust destroy and where thieves break in and steal,
20 but lay up for yourselves treasures in heaven, where neither moth nor rust destroys and where thieves do not break in and steal.
21 For where your treasure is, there your heart will be also.
22 “The eye is the lamp of the body. So, if your eye is healthy, your whole body will be full of light,
23 but if your eye is bad, your whole body will be full of darkness. If then the light in you is darkness, how great is the darkness!
24 “No one can serve two masters, for either he will hate the one and love the other, or he will be devoted to the one and despise the other. You cannot serve God and money.
God's word tells us in great detail how to live as children of God, as Christians. Nowhere does Scripture ever hint that gambling is okay. In light of the verses above (and many others that warn us against being at all preoccupied with the accumulation of wealth), you should not be gambling with God's money over which He has made you a temporary steward.
Matthew 6:31-33
31 Therefore do not be anxious, saying, ‘What shall we eat?’ or ‘What shall we drink?’ or ‘What shall we wear?’
32 For the Gentiles seek after all these things, and your heavenly Father knows that you need them all.
33 But seek first the kingdom of God and his righteousness, and all these things will be added to you.