There is nothing to be ashamed of regarding one's ugly experience in gambling. If it is an experience that you know you would not want to go through, it is better for you to open up to the person. You don't need to share your whole story, but you can give the person some advice on how terrible the journey is, rather than just keeping quiet.

In your own experience, it is possible that the reason why gambling was terrible is because you didn't have anyone to educate you; there were no opportunities. However, this person who needs your advice is fortunate to have you for a better experience in gambling.