To increase the number of merits, you need to increase the quality of your posts. There is no such obligation that you can earn merits just by posting. Even the number of posts has no relation to increasing the merits. To earn merits, your posts should be informative or helpful or skillful. If your post has an increase in any of these three qualities, then you can increase the number of merits. Or for some other reason, you can earn merits if someone likes your post and is willing to give merits. I would advise you, instead of focusing on other people's profiles, keep yourself busy in increasing the quality of your posts.