Join some bounty campaign in Airdrop is best way to earn that. Then after you get tokens. You can sell it in exchange thread in this forum. Don't forget to do Escrow to transaction with buyer. Because they are many scammer can scam your tokens
Airdrop doesn't help you earn that much. I suggest to join reputable campaigns. Right now, best option is to start mining bitcoin or join signature campaign that pays bitcoin. There's a signature campaign that pays bitcoin to participants by completing their task.
Suggesting mining in earning bitcoin is not actually a good idea. You need a lot of information before you start doing mining and the also the specs are very expensive, maybe the OP cannot provide most of them. There's a lot of ways on earning in bitcoin but make sure it is actually profitable not a waste of your time.