I think talking to the addicted gambler always seem to help in some cases and if that doesn't help, there are people that the addict greatly respects and it will be good to let those people know what's going on and when they talk to the him or her, they may listen to that person.
But what kind of things should i say to him? He respects me, but I don't think I'm enough, he has a girlfriend that he really loves though, and his family. He might listen to them. But it would really help if i could be able to say the right things.
Edit:
proper approach and continues guiding the person if possible not to allow him to be able to do his activity if you can always be in his side
for a while so you can monitor his activities and encourage him to divert his gambling time to a much profitable things maybe you just
need to think of other possible things to do for sparing your time.
But I cannot be always by his side because i have lots of things to do also, i could spend time with him but not that much. I think telling his family or gf would be a nice idea. Any suggestions on what profitable things i should introduce to him??