Let me give you an example. When you are doing something and you can tell it to other people without any hesitation or any fear of anything, you are doing something good. But if you have to hide something from someone or from the society, then maybe you are doing something wrong. So when you are gambling, are you able to disclose the information of your doings to others without any kind of issue? If not then maybe you are doing something wrong.
Depending on where you live and what you are doing, gambling could be good or bad for you. People mostly come into gambling to make money. When you have a mindset like that, you will most likely lose money in the process. That's why many people think of gambling as a bad thing. But when you are able to purchase the entertainment of gambling with money and whatever you invest into gambling does not affect your personal life, then you are good with it. It is created for the sole purpose of entertainment and you should use it that way. In that process if you are making some money, that's an advantage. But don't take it as main income source. Because it is based on luck.