My experience till now is surprisingly positive. I began to subscribe to airdrops 2-3 weeks ago and I already received 41000 Candy, 250 Poly, 1000 Jesus Coin, 100000 Mankind First, 2000 Refereum and some other. Of course many of them are worthing really few dollars (for the moment!) but some of them I reach to exchange for 100/200$. I found a really good website collecting information about Crypto Token Airdrops and it is daily updated:
www.airdroptracker.co I hope it can be useful