I've joined the airdrop over the past 3 months and I only get very little value from the airdrop, the majority of which I have to keep it to add value.
So how can I earn a few hundred dollars a month if the bounty is a good plan?

Most of the airdrops are not worth it, it is wort to participate if it is stake based, so you are like a founding member of the project, something elixir did. If it is fixed amount like a few dollars of course it cant be worth much. Even if it goes ten times up