At how many post when you got your first $10 in Mylot?

It does not go by how many posts. Mylot's payout is based on an algorithm. Sometimes you get one cent, sometimes more. Also it is the quality of your responses that determines how much you get paid. Your response should be at least 3 lines long and pertain to the subject. One liners do not earn anything. Furthermore, if one or more of the discussions you have responded to gets deleted you don't get paid anything. So choose your discussions wisely, make good responses and check your earnings to see how much you got. The earnings are updated the next day. They can go up or down a bit.