There are many types of airdrops, many where you'll never actually receive any coins, many where they'll be worthless, and some where you'll really get the amount that is kind of significant, or truly significant in some cases. As you get more experienced, you'll learn to find out how some of those (both good and bad) can be recognized, which to avoid and which to look out for. But it's not easy, there are no guarantees, there's no single place that I know of that lists only good airdrops... There are however places where you only get airdrops that are potentially worth only a couple of bucks, often not even that, and you can easily avoid them. To motivate you, I got a few airdrops worth hundreds of dollars, even one worth two thousands (if I sold at the top, which I didn't, and now that's worth $50 and I still haven't sold the coins). So another good point, you have to know when to sell, which is another thing you'll get better with along the way.