Yes, online slots casinos are trustworthy as long as you know where to go. The vast majority of online casinos are completely safe places where you can play and earn real money. However, there are some scam sites out there too. That's why it's important to understand the signs of a trustworthy casino site.
Most sessions on slot machines will result in losing money, and there's nothing you can do to chance that. Sometimes you'll win at slots, and even win big. Enjoy those times when they come. But never bet money you can't afford to lose, and be sure you're playing games that fit your bankroll.