Bitcoin Forum

If a newbie requires 30 posts to upgrade into a jr. member , how about the jr. member? How many posts I must post?
Thank you.

Your rank does not change with how many posts you make, but with how much activity you've got.
Activity & how much you need for all member groups are explained in this thread: https://bitcointalk.org/index.php?topic=237597
After Jr. Member, you need 60 activity points to become a Member. Therefore, you need 30 days of which you've posted at least 1 post per day.

The core value here in Bitcoin is not just about how High your Rank is..But What Knowledge and wisdoms you have learned here and how you socialize yourself to the other CryptoUsers...Hope all would value their knowledge here and A lot more Would share their experiences to us Newbies

Take a look...everything is explained in this
https://bitcointalk.org/index.php?topic=178608.0

Your rank will not change even if you post more and activity the basis for you to rank up and if you really want to grow up fast you have to wait every two weeks to increase your activity of 14. And you just need to be patient for rank up and now Jr.Member it can earn by joining signature and bounty  campaigns

If you actively participate in the life of the forum and help people, then in a month you will cope with a new rank and feel yourself in a different guise. The main thing is to work hard as elsewhere.

Upgrading to another level in bitcointalk forum is not very difficult but I advice you to make sure you go through the forum rules thoroughly to avoid being ban along the line.

I also do not really understand the purpose of ranking, post and activity how does it mean?

I registered in 2015 but did not care about the rank and was not active on the forum. Now I regret that I did not do this, my rank could be higher.

Here https://bitcointalk.org/index.php?topic=237597 you can find all informations about the ranks
It depend on your posts number and how long you have registered the account
I can recommend you to not make unnecessary and off topic posts, make only constructive and quality posts

It is the activity that's being counted in order for you to rank up. You need 60 activity for you to rank up to member. But mind also your post quality, don't forget that you have to post constructive and something thay the community will benefit from. And always follow the general rules and guidelines so that you will not be ban eapecially when you are part of a signature campaign.