Island expeditions are very easy to complete while leveling, particularly before hitting Level 116 when your legendaries are still in effect and your secondary stats have not been squished by leveling scaling yet. Island expeditions can be completed in 5 to 10 minutes relatively reliably while also acquiring some of the pets, mounts, and Bind-on-Equip gear available. There is also one weekly quest to do one island expedition, so for slowly leveling alternative characters, be sure to complete at least one island expedition each week.
Elemental items (Primals, Eternals, etc.) can be a good source of money, because they are always in demand on the AH. See which mobs you will most benefit from farming, then set out for a few hours. In the process you will also most likely collect significant vendor trash, and may get other profitable item drops as well. Note, however, that older elemental drops usually lose profitability compared to newer ones, i.e. Primal Water sold well to level 70 players in BC, but sells far less well to level 80 players in WotLK, because level 80 gear requires Eternal this'n'that.
Highmountain tauren - "Descended from Huln, brave hero of the War of the Ancients, the Highmountain tauren honor the spirits of earth, river, and sky. Though the Legion invaded their lands and sowed seeds of distrust between them, the tribes of Highmountain stand united once more. At long last they are ready to venture beyond their sacred mountain and stand beside their kin from Kalimdor, lending their nobility and strength to the mighty Horde."
This is by no means a complete strategy, just a bit of insight into how I believe many approach transmog incorrectly and burn themselves out on it before they can succeed. There are better ways to do this, and you're free to pump as much time as you'd like into it to try and improve the results. Whatever the case, just make sure you're enjoying yourself, because it is that much easier to stick to when it's fun.
The Horde 12-20 (Barrens + Stonetalon Mountains) guide has been rewritten and revamped. In addition, there has been numerous tweaks to the speedrun route to make things faster and easier to follow. Also, in case you haven't noticed I am now adding about 40% more info per step and redoing all the images. Unlike with my previous vanilla guides, I am now giving a brief explanation of where to go and what to do with each step along with any other helpful tips.
Similarly, when earning by volume, do not overload the AH with your items. Basic supply and demand: too much supply will make your wares too common and unwanted. Furthermore, with great demand and a cheaper price, you may end up starting a price war with your competitors, with them actively trying to undercut and outdo you. Moderate the amount of items you're selling on the AH to small batches, refilling them only when sold out.
Now that we have a lot to post we reached a point where we have to plan what items we post on an 12-24-48 hour cycle. The auction house fees for Warlords of Draenor items are extremely high. And the values of the items are really screwed up. A lot of the weapons or armor has an item value of 5-10.000 Gold. But they look plain bad and the chances of selling them is pretty low.