You should not convince people that gambling will be a quick way to make a fast buck. Gambling is profitable only in sports where you can get a slight edge over the bookmakers. In casino gambling, you will most likely lose your money in the long run so if you wants to introduce gambling to someone, you need to warn him/her on the risk he/she is facing.
I can imagine how gullible someone that would get convinced based on something like that would be to have gotten convinced in the first place. Anyone in their sane mind will not be ready to accept that gambling is enjoyable and even if the OP decides to do that by convincing someone, I would say that is exactly what he believes and that could even come up in an argument for him and each person sure have what makes them tick as far as I am concerned.
However, it is always much matured when as you are letting people know that gambling could be enjoyable which is true if you perceive gambling the right way and not chasing some wins except to catch some fun, then in that case, like you said, it is better to let them understand the risks involved as well.