The minimum post to earn merit is one post. You can make one post and earn several merits if the post is very useful and helpful. You can make hundreds of posts and no one will send merit to the posts because they are useless or of low quality.
Read what good posters are posting and start being like them. Post something useful and help.
Absolutely right, posting what actually attracts person and it gives meaning to others who are reading it, not by how many post will give us merit but how educative the post is.
That is why it's essential to read the rules governing this forum, so that we won't make a mistake or go against the rules and also it's okay if to more research and be sure of what we want to post before posting it out and also read it to be very sure of our words.