You don't need to leave your original Wholesaler society, you should stay with that forever. The merchant in there sells all the basics you need for crafting through all the levels.
In the same suburb you will find a Scholar Society; it will be a door somewhere, maybe even inside another building, with an NPC next to it to apply to. All the Societies are shown on your map and you'll always belong to 2, your original Wholesaler and your specialist Workshop.
To get your level and title of Sage all you have to do is craft one more item in your chosen profession and you'll ding