Seeking the advice or help of concerned family members and friends could be of great help but sometimes they are limited because most of them lack the needed counselling skills.
Help from family members will be the best since family members are closest and also understands that estent of damage such attitude has brought upon such person. The only challenge is that, most people don't bring family to the cause of the damages they effect, they tend to hide it away from them knowing that family needs no approval to activate a corresponding correcting measure on them.
This is a good option but we can still have to consider that not everyone has the interest of considering the family members once it comes to their kind of way of life in gambling, but those that could help in this kind of situation are most likely the family members because they cannot afford watching one misbehaving and they do nothing about that in their own capacity, this means as a gambler, we should also value our family because when things turn up side down, they are our last hope
My first advice in this regard is for the person to fight by himself. You have to first admit that there is a problem and fight within you, that makes you a man. I Mention "man" not because this approach is not applicable to women too but to characterise the mind battle and winning as being manly. No one would help you more than you help yourself and I've seen a whole lot of addicted people who fought and won easily all by themselves just because they are serious and determined to do it.
This is mostly applicable to those who are of a strong mind, but if you are such that is of a weak mind, my advice for you is to quickly find help. You could tell friends or family or get entirely external help from a therapist.