well..tbh...it's 400 motes at any level
I think I figured out the most efficient way if anyone else is farming.
1) Do all 5.0 world bosses every week. Start the raid on a level 1 then spam trade or openraid for World Boss tour. Galleon, Sha, Oondasta, and Nalak (you will have to be summoned to him) - it sucks when you get gear, or in my case Son of Galleon mount which you can't learn ><, what you want is what everyone complains about getting...the box drops. They
can contain large amounts of motes (I got 18 once).
2) Do all 5.4 world bosses every week. Start the raid on a level 1, then you can invite people through other raid. Both the Celestials and Ordos (easier if summoned to him) can drop the same thing as 5.0 bosses
3) Go to Guo-Lai Halls in Western Vale of Eternal Blossoms. The mobs respawn really quick, once you clear 1 room, the previous one has respawned. In addition to motes, they can drop Ancient Guo-Lai Cache keys. The keys open up the chests in the Northwest vault. The caches can contain full Spirit of Harmony, and a chance to have a Treasure of the Vale which can contain motes or Spirits. In addition, the mobs can drop Skyshards to help with your Alani grind. I was incredibly unlucky and only got 1
4) When you're bored...you can always go around and kill the old quest rares that spawn relatively quickly in the Vale. Again they have a chance to drop motes, treasures, or skyshards.
5) All of its random, so mileage may vary. It took me a solid 15 hours of game play to get mine.