Do I understand right that I need to be minimum a Junior member and then I can join the bounty? Or can I go for airdrops until I have become a junior member? It would be a good way to support the idea also
That's basically how this forum works. Signature bounties are not available to new members (newbies) you have to attain a higher rank to be eligible for signature bounty.
But I guess if he have more than 500-1000 followers on twitter/facebook then he can join twitter/facebook bounty. He have to check on their forum.