Not sure what you are asking here. I think you might mean how many tournaments a month can a player participate in? If that is the question, the answer is as many as you want.
On the other hand, if you mean how many tournaments a month can you sanction, it depends. PTOs can sanction as many as hey want. Other TOs start out being able to sanction 2 at a time, so they have to wait until one is completed before they can do another.
As to rankings, if you win, your ranking goes up. If you lose, your ranking goes down. It really has nothing to do with how many you participate in.
BDS