As far as I understand it there is no need to introduce yourself after registration. Though this is not a bad thing to do. I don't read many boards or forums. In smaller ones I always appreciated some kind of introduction of new members. But that were boards with a few hundred members, probably more localized, less international...
This Bitcoin forum is another beast.
Write what you like to share with others. It might be a substantial post. This seems to be the required thing to promote you from being still a newbie.
Would be interesting to figure out what makes a post "substantial". A certain number of sentences? A certain minimum length, together with a certain number of sentences? What makes a sentence, dispite the common grammar rules?
Oh well, too many questions. (I don't expect answers. Though I wouldn't mind getting some!)