Yes newbe is not allow to join a signature campaign.
rank up  your status into a jr.member first before you can join the bounty campaign.

Yes of course increase the rank junior member to follow bounty program,  it is he rule of manager project bounty program although in a part newbie can join bounty program but it is so many scam.

Unfortunately, Yes newbie cant join its because to avoid spamming, But I heard that there are some campaign who accepts newbie, So look for one and make sure to rank.

Very convenient service from bounty managers community https://bountyhive.io/
Really good for easy participation, but now only 4 bounty avialible.

Hi,  i'm also a newbie but I can still join bounty campaign like Facebook, twitter and Airdrop.  There are some campaign doesn't required to be a member for you to join.  You can still earn stakes through social media campaign though it will not be
High like for signature and other bounty campaign that does require to be a jr.member atleast before you can join. You just need to look thoroughly if you want to earn stakes as a newbie. 

Can i use my facebook to join bounty program? My fb has 2k friends

Most bounty programs doesn't accept Newbies, I know I'm a Newbies as well. Even if they accept, bounty given is so low.

As a human being when your mother gave birth to you did start walking immediately no so that is how it is here you need to start from somewhere and as a new person in this place you need to start in the beginner and help.

Yeah, exactly for most cases! The reasonn is there are tons of newbie accounts in the forum. Some account are created from new users, otherwise some accounts created by old users, who tried cheating the system with lots of faking ones. Those sort of faking accounts used only for cheating money from bounties, airdrops, campaigns, etc in the forum. That's too bad.

https://bt.irlbtc.com/view/2818350.0

New merit system launched by admin of the forum, Theymos, might solve that issue related to newbies.

The fact is you can join surely, but the problem is there are very little projects which open their bounties for newbies.

It is aslo due to the fact there are thousands of newbies in the forum, part of them, try to cheat and get free money from the projects and bitcointalk forum.

So you should contribute good posts to be ranked up to at least Junior member to join those ones.
Good luck and be a good member in the forum in positive way.