now, is it 30 activity to become a junior member? and are campaigns for junior members or mostly for members and up
Yes.
There are only 2 campaigns for newbies and jr members, and a few more for members+.
Please check
https://bitcointalk.org/index.php?topic=615953.0 for everything you need to know about those sig campaigns.
777 is my best choice as a junior member, but how do i join their campaign? do i have to make an account with them or what