Based on my experiences, it is very hard to earn merit amidst making a quality and useful post. The standard is just very high and I think there's a certain place where you can earn lots of merits and I haven't found it yet. You can actually buy it but I think it is not safe, there are moderators who often check if the post is really worth the merit. Try finding more giveaway threads and make sure your posts are well related on it so that you can earn the merit you are longing for.