Look mate, there is a saying in my place that 'he who is not ready to save himself, nobody can save that person, no matter how hard they try', being a friend to an addict gambler does not mean you should turn yourself to a babysitter, most especially in a case where the addict him or her self isn't even a baby.
Don't get me wrong though, its not a bad thing to try to help, after all the biblical law commands us to be our brother's keeper, but then, you can only help someone who is willing and in need of help, else your effort will just be wasted one, and if not careful, you might even end up becoming an enemy to the said or supposed friend, this opinion of mine is based on personal experience though.
I think what a gambling addict needs is genuine attention so that he knows that there are still people who try to be kind and care about him. Gradually, this will open his heart to accept the person, and with this gentle approach, the gambling addict can start to open up. After all, there's nothing wrong with trying to pay attention to a gambling addict, especially if we know them well and we think they really need our help.
What you said is very correct bud, i totally get your point, But then, what i meant in my comment above is that, there are some people, regardless whether we know them or not, that have made up their minds, maybe not forever but for that moment, and nothing you do or say to them will make them budge, and if you with your really genuine intention to help try to push harder to make them realize you are only trying to help, they either pick up a fight with you, accusing you of trying to control them, or they start keeping distance from you..
What i am really saying is that, for your help to be really effective on a gambling addict, or some one with any kind of problem that they need help with, they(the person) have to first of all admit they have a problem and need help, this way, they can genuinely value your help, and you also will be very motivated to help.
Aside this, how do you convince a gambling addict that he needs help, when he or she does not even know, or ready to accept that he or she is addicted?