First, gambling breeds a form of covetousness. The Tenth Commandment admonishes us not to covet. Coveting, greed, and selfishness are the base emotions that entice us to gamble. I believe Christians should be concerned about gambling if for no other reason than the effect it has on the weaker brother and how it will affect the compulsive gambler. State-sponsored gambling makes it harder for the compulsive gambler to reform. Legalized gambling becomes an institutionalized form of greed.
Therefore no tith can be paid from money obtained through breaking one of the 10 commandments!