What makes you think you will be able build every building in your Garrison?
First off... layout:
From what we currently see here, (subject to change) there are 11 plots total for you to fill it seems from this. One of them will automatically be your Inn/Town hall, so that's 10 left to fill.
Now, lets count the professions:
Alchemy
Jewelcrafting
Leatherworking
Blacksmithing
Engineering
Tailoring
Inscription
Enchanting
Mining
Herbalism
Leatherworking
Fishing
Archaeology
Cooking
First aid
That's 15 (FIFTEEN) professions!
Now, we can subtract one of them because I believe they stated that the Inn will house the Chef for Cooking...and I'd be REALLY surprised if there's a first aid one...
This leaves us with 14, possibly 13 if First Aid isn't addressed.
Now, are you ready for this?
On top of this, there are additional types of buildings OUTSIDE of professions that you can build. Two of them we've been told about is the Barracks that let you house more followers, or the infermary which speeds up your recovery rate of followers (Could also be the first aid building!). They also have listed there a Storehouse, Salvage yard and a Dance Studio (These are VERY unconfirmed and are most likely placeholders... but still, there will be more than one kind of building)
So... there ya go. So far it seems like you cannot get all the buildings in your garrison. One person might have their garrison focus soley on Follower aquisition, housing and ability to allow them to send them out on more missions to get themselves more gear. Another person (such as myself) might focus on professions as they're 150% casual (My first one is the fishing pond... HANDS DOWN!!!!! ^_^)