The Elder’s Manual seems to say it two different ways.
I. Gambling is to be avoided in all it’s forms.
(Shepherd the Flock of God, p69 (the 2010 Elder’s Manual))
“Christians should avoid gambling in all it's various forms, including lotteries. If a person makes a practice of gambling and after repeated counsel unrepentantly pursues a course of greediness, judicial action would be appropriate."
II. Petty gambling for entertainment is ok.
(Shepherd the Flock of God, p70 (the 2010 Elder’s Manual))“The elders do well not to involve themselves in what individuals do with regard to petty gambling solely for entertainment. They may need to give counsel if this becomes a cause of stumbling for others or affects the spirituality of the individual or the congregation.”
Once again the Organization seems to be saying it both ways.
It seems so unclear these days. I guess they can get you if they want you, but if they want to let you slide they have a basis for that too.