How do I trigger the initial garrison invasion?

[gewdgewd]

My brother and I have each leveled three characters to 100 and have not yet seen a single garrison invasion. I feel like we're missing something major, but I can't find any information on how the first one appears. Is there a quest or something somewhere that chains into the invasion? I've completed the entire FFR storyline, so I can't figure out what is missing.

[Tradu]

When you upgrade your Garrison to level 2, you get a sort of tutorial invasion. It doesn't give any rewards, it just shows you how they work. Real invasions with bronze/silver/gold medals and actual loot are completely random at Garrison level 3(iirc)
The level 2 invasion has happened for me on every character I got to a level 2 Garrison(5 so far) except my monk, which didn't get it because I levelled it while the servers were completely fucked, so it never triggered, I assume. It triggered after I finished the quests to unlock the level 2 Garrison and went back to upgrade it if that matters.

[Roundhound]

They arent random, they just require a lot of farming of a certain faction. If you do the Scorthear (sp) Rise Apexis daily 5-6 times that should give you enough kills to trigger the shadowmoon invasion. I heard its around 500 kills to trigger an invasion.

I believe I saw a youtube video, but I didn't watch it, with a brief tutorial on them.