One of the most dreaded things about leveling Enchanting is the terrible Greater Eternal Essence - Illusion Dust stretch. These mats aren't just expensive, they're also rare, and thus usually in short demand. This means that even if you can afford their exorbitant costs, there simply might not be any available for you to buy!
And unlike the other dusts and essences, you're quite unlikely to have randomly picked up more than a few during your questing/dungeoning. Enchanters pushing through this horrid phase can expect to dish out a LOT of gold for these elusive materials.
However, there is a better way! All it takes is a little travel and preparation to easily get around these hated mats.
Formula: Enchant Shield - Greater Stamina
Requires Enchanting: 265
Rurns yellow at 285, turns green at 305, turns grey at 325.
This enchant takes a mere 5 Dream Dust, which are very common and usually very cheap on the Auction House, making this an extremely inexpensive way to get a good 60 points. Yes, I'd recommend using this all the way until it turns grey. Even with a bunch of enchants where you didn't gain a point, there's a good chance it'll still be cheaper than your alternatives. (Depending on your server's Dream Dust market, of course.)
Horde players can buy this recipe from Daniel Bartlett in the Undercity, while Alliance players can get it from Mythrin'dir in Darnassus. It's Bind-on-Pickup, so you have to actually go there on your Enchanter.
The recipe is limited-supply, but apparently if you buy his other limited-supply recipes, the Greater Stamina one might show up soon after. I haven't tested this, mind you.
Of course, if you want a change of pace, or perhaps you ran out of Dream Dust, here's another option for you.
Formula: Enchant Chest - Greater Health
Requires Enchanting: 275
Turns yellow at 295, Green at 315, Grey at 335
This enchant requires 2 Small Brilliant Shards, which are virtually useless, being only used for this enchant, Enchant Weapon - Icy Chill (which no one makes), and a trinket which hardly anyone knows about/bothers making. As a result, they're usually very cheap on the AH, sometimes almost free.
Yes, that is a stack for THIRTY SILVER.
Both factions can buy this recipe in Everlook from Qia, a goblin Trade Supplies vendor. (She's in the same building as the neutral auction house NPCs.) It's not bind-on-pickup, but it is limited-supply, so you might not get it your first time out there.
Added bonus? This enchant is a very good enchant for twinks or heirlooms! So not only is it cheap to produce and great for leveling your Enchanting, but there's a decent chance you'll be able to sell it for some reasonable profit, too!