I'm not one to automatically think that all gambling is sin. I think gambling is like eating or sex, it can be sinful if we don't exercise some self-control with it. We all have what's known as "disposable" income. If one drops $300.00 playing poker, I don't think there is any moral difference between that and dropping $300.00 a year on cable TV or eating out at fancy restaurants.
The thing is, before we go disposing income in wasteful ways, are we meeting our financial obligations, both to ourselves, our families and our communities.
I wasn't joking about there being many families that cannot even put food on their tables right now. If we have enough money to blue on gambling, renting a bunch of movies, or eating out, we could most likely use that money much better by donating to the local food banks.
This isn't to say that everyone who is disposing income in wasteful ways aren't first taking care of all financial obligations, and giving to the needy and their churches. What one does with their finances is between them and the Lord. Nor are we commanded to give.
Just keep honest about it. Don't be like Annias and Sappharia, who acted like they were disposing a lot of income for the Lord and yet keeping it back. Give, or don't, waste money or don't. But, whatever one does, do it as unto the Lord.