In my opinion, the easiest way is to invest in the first 5 currencies from the top. In this case, you don't need to do anything. But it will bring you profit over the next few years.
You are right but I have various sites without investing in these first 5 coins in this forum Bounty, Airdrop Signature Promotions etc. You can also earn some of these but you must have knowledge of work before working.
Referral program can also be added, just make sure to refer only legit websites and research whether they really paying every refer you make. There are also application add ons that are use to earn some token by installing or watching ads.