Initially, I use to think merit is by chance ( i.e something that will just happen) or lengthy article ( i.e writing too many paragraphs and the rest of them), but I have come to realize that, it is more than that.
I have being discouraged several times because of my numerous posts and replies yet no merit then. Even now, some times I use to be discourage. However, the only way to get merit is by posting quality article ( that is what determines merit) which almost everybody is aware of now.
In summary, don't look at the quantity of post you have make so far but instead try to adjust, I mean improve in your posts, above all be consistent and patient that is the key.
You're correct that making quality replies and posts does earn you merit, but you also need to understand that asking questions that are crucial to ask can also earn you merit. Merit is similar to an award given for well-done work, but in a forum, you shouldn't always expect everything you do or the thread you start to earn merit. If you do, you'll get discouraged, and that's what gets newbies in the forum.
Additionally, when creating a thread in the forum, consider not only what will benefit current members of the forum as well as those who will join in the future. Sometimes, merit will find you; other times, you will need to let merit find you. The more threads you create that, if read, readers will find helpful, the more merit will find you. My best advice to you is to never give up.