The best way to make tons of money with inscription is by making Darkmoon Cards of Destruction, and using the resulting leftover Blackfallow Ink for glyphs. For instance. On my server, you can buy a stack of Whiptail for about 23g on a good day. On average, you get 1 Inferno ink (2 Burning Embers) per stack of 20 Whiptail. A darkmoon card costs 10 Inferno Ink, a Resilient Parchment, and 30 Volatile Life. The Volatile Life goes for about 10g each.
So in total you’re looking at about 530g to make 1 card. The cards are random and can go for anywhere between 500-1500g. Now, you may only break even with the card, but you’re left with quite a lot of Pigment left over from milling. This can then be turned into glyphs. The glyphs take 3 ink and 1 parchment each to make, and can sell anywhere from 10g-150 each. If you pick glyphs that are currently selling at high prices on your server (only make 1-2 each, that way you’ll have a lot of variety), you can end up making an extra 1500-2000g off of that stack of herbs that was bought for your Darkmoon card.
Also, if you are an herbalist, there is an awesome location (pictured below) in Uldum that I use for farming Whiptail. In an hour of farming, I can get around 15-20 stacks of Whiptail from following this route.