depends on his/her history and depends on what kind of connection we have. but generally i will help him with the amount that i'm not expecting to be paid back.
There are so many factors that have to be considered before people start helping someone in the world of gambling. Definitely if you know the individual personally and know he or she is really in trouble, you will try to go even out of way for helping them because it is a social service as well. But if someone is not willing to change and is simply trying to gather money for more gambling, no one would help him.
Today another option came to my mind that if the person will want help and he is saying that he need this help because of his family and want to feed them and in this case you have doubt on him then you can can buy goods and food for his family and can send them to his home to his family. That will definitely help that person in real means and you will not worry that you helped someone in losing his money in gambling.