For some reason this post was flagged as inappropriate and hidden for violating terms. Not sure what I did, but my best guess is the link, so I pulled that.
My son sent me (removed link) since he knows I am a bit nuts on garrisons.
The scheme is basically to do a table mission from your garrison once a week to get an invasion active, then just afk complete the invasion with your 120. Apparently guards spawn at your level (120) and mop up on the 100s. You can push it along to make sure you max score, and you get the reward chests. If you have a trading post, you can get parts that way which can sell (but are hard to sell) for several thousand gold.
The main thing that occurred to me while watching that video was using the trading post to convert extra garrison resources into fur, which sells on the AH and fuels the 30 slot bag market. This might be faster than doing the trap/barn routine, and give a little more flexibility.
The other thing I am going to check on is the blazing firehawk battle pet. You can buy them for 2K apexis crystals, and if you can cage them, that might be a good way to convert apexis to gold via the AH. You do need exalted with Order of the Awakened.
Once you have around 6 followers with extreme scavenger, you generate so much Garrison Resources a week that you need to dump them somewhere.
I do not think the Mage Tower is worth it over the stables though (as per video)