#3 - Aug. 9, 2014, 6:02 p.m.
When you complete the quest Bigger is Better and upgrade to garrison tier 2 you should receive a book of garrison blueprints that will teach you ALL level 1 small, medium and large plot buildings.
Level 2 requires you to either be level 98 or to have completed one of the following Spires of Arak quests: The Ebon Hunter or No Time to Waste.
Level 3 are all unlocked via various achievements.
You do not need to do the Gorgrond quest to unlock the blueprint for LM or Gladiator's Sanctum.