but also need to increase the number of my posts. In this way, it is possible to get more merits.
Increasing the number of your posts does not put you in a better position to get merits, only the quality of your posts matter. Making the effort to post more than you can, could even be counter productive, reducing the quality of your posts as you are trying to create more.
Posting naturally is one of the best methods to maintain quality, reason why most campaigns either put a low post requirement or no requirement at all, allowing members posts the way they can.