You could use TSM and get a snatchlist from google so you'll get an alert everytime an item is under 100g
Always check the TSM alert for blue's and green's that you can undercut.
Lol, don't sell them to the vendor?
Example: Yesterday I got the MoP Sandals, not sure what the exact name is, for 100g. Flipped it for 5k within a few hours.
Basicly every retardedly low Blue/Transmog that is under 100g you should buy and resell. I don't know the exact prices for every transmog and blue but google is there for you.