As you guys don't know each other properly so it won't be wise to start conversation with him directly about his gambling. He may feel uncomfortable when a stranger randomly start advising him! And if a person can go to casino for playing slot machines, then i assume he already have knowledge about sport betting too. So he may play slot machines for fun even it is also possible that, he isn't regular in gambling.you still don't have the actual information at all. So whatever you can do, just frankly start talking with him if you are excited enough. And then you may ask him about his opinion about gambling and if he does gambling or not. Thus you can discuss with him and let him know about your opinion, rather than advising him directly
Looking at the continuation of the Op's response, it sounds like they're beginning to be friends, and discussing more on gambling related matters. If they could work together that wouldn't be much problem. Talking frankly with the player is the right thing, so that he wouldn't pick up some argument. Gambling is a matter of choice, and he's quite okay with his slot games, despite being a sport man. I don't think any of the is doing the wrong thing, but Op shouldn't cross his boundaries.
Money mostly change our decision and same as our attitude , if they are good about it then better to talk and act together for their own betterment .
while one is in slot gaming but for me Sports betting is much better choice in gambling because of the higher opportunity of winning than luck based game.
I also prefer sports betting because in sports betting people can spend hours analyzing the games and, if they have good skills, they will be able to get the bet right and make profits. in other words, it is a bet in which the greater the person's skill, the greater the chances of the person being successful and making a profit, which is why I don't get involved in gambling that depend on luck, I prefer to just focus on betting sports. Looking back I remember how sad it was the only day I played a gambling that depends on luck, I spent many hours playing, I made a 3x profit and instead of stopping playing and withdrawing what I had already won, I continued playing and started losing steadily for 2 hours and in the end I lost everything, I was wondering how it was possible that I had played for many hours
That day I understood something that scared me very much: not to play gambling that depend on luck, because I saw that I would go down a path to the abyss if I were to play any gambling that depends on luck again, and Since that day I haven't played any game that depends on luck, not even in the real world I don't play anything. I only focus on sports betting and only on football games and the main leagues in Europe because I can only spend a short amount of time playing gambling, I rest a lot, I've had a lot of time without playing, so my self control is very good that way, while the People who play games that rely on luck spend many hours playing and can easily become addicted