I have done 30 activities, but my rank is still a newbie. I thought after doing 30+ activities rank would be increased.
Your questions contradicts each other let me explain what I meant. First you ask a question only a old forum users or someone that knows how the previous ranking system works will know.
How does the new ranking system work? How can I increase my merits?
Then you ask another question first acting like you don't know how the new system works but again you asked how to get merit (that serves as a requirement) in the new system.
OP you're trying to play smart but lets say you're truly asking like someone who doesn't know then read this thread;
FAQ: Everything you need to know about forum 'activity, account ranks and merit
And if you feel you have written some quality posts that went unmerited due to one reason or the other, participate in;
UPDATED [20/02/2019]: List of Active Merit Giveaways threads.