Well i have an experience wherein my friend which happen to be addicted in gambling and as we notice he can't stop in playing because he's reason is that he believes that he can recover it's lost and get more money but it's the opposite he just ruined his own life and suddenly drops in school because of financial problem, we tried to stop him, but when a person gets too addicted whether who attempted to stop him he still not stop and the result is fatal.
That is what people get if he still playing gambling because gambling soon or later will ruin his life, as you said. That will be a sad story, but I hope that your friend can learn from his mistake and try to raise his life. We can help him to get out of gambling forever, but that will need a strong effort from him so he can say NO to play gambling. We can suggest him to do another thing, and maybe he can start to work in real work and make him busy every day, so he will not think about gambling anymore.
The addiction of gambling is so bad that at times you need proper treatment and medication in order to get over your cravings for gambling. Your friend if is unable to differentiate between his losses and gains from gambling, then of course he needs some medical support. Simply by getting him involved into some other activity or by diverting his mind for some time, you cannot make him forget gambling.