Do i rank up instantly when i have 30 posts and 30 activities?
There's a thread at the top of this forum page (where you posted your thread) titled
Newbies - Read before posting. You should read this.
Rank updates occur every two weeks, provided you've achieved enough posts and time served to reach the next rank up. There's a lot of great insight here, much of it has been discussed so be sure to check or search for threads that answer your questions before you start a new thread.
Good luck to you!