There are different airdrops, some where you'll never get any coins, some where they'll be worthless, and some where you'll really get dozens, sometimes hundreds, and if you're lucky, even thousands of dollars. Try to look for bounties instead of airdrops, where you have to invest some time and promote the coin (a bit more than do a single retweet or similar), those pay more and again, if you get lucky, some used to pay peoples' mortgages back in January. You also have to sell in the right moment, near the top of the cycle, and the new cycle just keeps getting delayed