How should my post quality be?
I'm not a teacher. If you are not able to research and understand this issue on your own, then you have no place being in this campaign. Read this:
Campaign EttiquetteIs it possible only local post?
No. You will get banned very quickly if you do that.
what about a constructive altcoin writer? who write in Global forum also but the most posts are in altcoin section (I am talking about my self of course)
Yes. The altcoin section consists of 5 boards (whereas a local board is only 1 board) and I can evaluate your posts easily.