Newbies can paticipated almost in all Campaign, but not for signature Campaign, usually the requirements to join Signature Campaign is at least Jr. Member and above, thats because every rank in this forum have its own limits to put signature, read more :
https://bitcointalk.org/index.php?topic=178608.0But for joining the Bounty Campaign, all rank can join, except rules from the bounty manager, but since I joined in this forum all rank can join the bounty Campaign.
For more clear :
• Work by bitcointalk account : requirements is your rank, minimal Jr.Member and above, because you work use you bitcointalk account.
• Work by Social Media account : requirements is your social media account, like followers, friends and etc, Because you work use your social media account not use your bitcointalk account.