If I have a few mins to kill during the day (usually when waiting for ETH/BTC to hit the exchanges from my wallet) Ill sign up for an airdrop or two. Most of the ones that I have either haven't hit exchanges or are worth under $1.
TRON (TRX) was the first one for me that actually did something.
500 free TRX peaked at ~$30 and is currently worth ~$19
HODLing!
Airdrops are only for beginners who want to get their first coins. The value of such coins is minimal. From this there is no real profit. Airdrop is like a lottery with a small chance of winning. You will lose your time...