Poker is sport. It's a game of skill. Casino is just an entertainment. But it doesn't mean it's bad. Just remember that you will never earn longterm in casino. You are spending money there like you would in a cinema, sport event etc.
Casinos in general are pretty fun. You can go out with friends, you can smoke a cigar inside, drik free alcohol and have a lot of fun. And it's not that expensive.
Assuming that you play
roulette and you bet 10$ on every spin. On average you will lose about 30 cents on every spin. If there are 20 spins per hour you pay on average 6$ per hour. You would probably spent more just staying in a loud and uncomfortable pub. Of course swings can be big - sometimes you will lose 300$ sometimes you will earn 200$ or so. In the distance you will be behind but not more than you would be going to a cinema or a pub. Of course if you are responsible.