I only played beta for a week or two, and there's lots about the Garrison I didn't figure out in that time. There was a HUGE NPC named Garrison Ford nearby who would grant you resources as fast as you could click (early on at least), so I didn't get a real flavor of the effort involved either.
Anyway, if you want to prepare a bit for Garrisons (you get one nearly right away...) the best guide I've found is here:
http://www.mmo-champion.com/threads/1599068-Comprehensive-guide-to-building-up-your-Garrison (converted to a Blog as well, see link within).
The TL;DR version for those of you interested in focusing on leveling:
Garrison Level 1: Build the Enchanter Study (if you aren't an enchanter) so you can DE stuff as you level and build the Barracks (default building I think).
Garrison Level 2: Add a Lumber Mill so you can gain Garrison Resources (GRs) by collecting lumber as you are out in the world leveling. Add the Salvage Yard at 96 (but don't open Salvage until the Salvage Yard is Level 2).
Garrison Level 3: Available at Level 100... so nothing to worry about while leveling up.
Garrison Calculator: http://www.wowhead.com/garrison-calc#AkUlIAU
If anyone else has other Garrison info, please link to this thread! It's a bit overwhelming at first... a MoP farm on crack.