It depends on Money that they use for gambling. if the money came from a illegal job etc then that's a dirty money because of addiction on gambling some of people doing illegal just like rubbery or etc for just a small amount of money and they try to gambling it.this kind people are those who have a small source of income, and it's depend on what gambling their have and Status of Life they have.
That's almost a perfect statement, if the money spend on gambling is from some illegal activities then it can be termed dirty money. When the same is being spend from one's hard earning then it isn't dirty. I believe Op have missed, easy money is dirty money indicating the earning out of gambling as easy money. As for my view, earning out of gambling is not at all easy money. To earn that users undergo untolerable pressure because we've risked to get back an earning.