Per writers of 3rd ED:
For Enchanting, you need magical materials worth half of the item’s listed Cost. These can be anything you find feasible, and you can simply buy these. You can even buy an item already imbued with True Elements, but this might mean you’ll have to pay the Elementalist who wove it in addition to the cost of the True elements.
The thing since ED3 is, though, that you don’t need True elements in matrix objects any more. Since ED3, what you use to enchant is left open.
The Spell Defense of such a base item is normally unimportant, because you don’t use it in the process to make tests against. Or usually, anywhere. If it ever comes up, it would be something between 6 and 12, though.
Wizard makes a normal Spell Matrix Item (SMI). He has the relevant talent knack for it.
As a first step, he looks up the characteristics of the item in the PG. But because the RedbRick types are only human, they forgot a couple things and he’ll have to go to the errata too.
He finds that a SMI has a Spell Defense of 12 and a Cost of 2,000.
This means he’ll have to make his Enchanting Test against a DN of 27 (12+15) and use materials worth 1,000 in the enchanting process.
This will be a hard test, but the Wizard knows that the more he works on the item, the easier it will be.
He decides to craft the SMI as a robe made from the pelts of flesh eating squirrels, which means he’ll have to hunt about three dozen of them. The pelts also represent magical materials worth 1,000, so this covers his cost, it’ll be replaced by the time he spends hunting the beasts. He’ll also make the robe himself with his leatherworking skills and adorn it with all sort of buttons and the fashionable arrangement of differently colored pelts. This means he’ll have some modifiers to the Enchanting DN:
-1 for gathering the pelts
-2 for crafting the robe
-3 for an excellent result on leatherworking (artisan)
which brings him to a DN of 21. Still a bit high.
He decides to design his personal crest to add as a brand to the robe, and to then spend 3 extra months on the actual enchanting, this further modifies by:
-1 for a symbolic element
-3 for the 3 extra months
for a total DN of 17. He can make that with Karma easily, without even using a blood magic boost or somesuch. After 4 months total of Enchanting, he rolls against 17.
If he succeeds, he’ll have the item.
If he fails, he won’t, but can try again, investing the time again.
If he has a Pathetic Result, everything is ruined.*
*This doesn’t happen if you use True Elements, they are very stable. Which is the big advantage for Elementalists. (Plus, elements are easily divisible, like coin. If your magical ingredient is a dragon’s egg, you can’t split that up…
There’s normally no requirement to use True elements in thread items, though.It’s just convenient and safe.
(This is all very complex and I don’t have that much time to put into it, but keep in mind, there’s only really three things you need to know: base Cost, Enchanting DN, and whether or not you can make the item as a result of your Discipline (this covers mostly blood charms and blood charms as weapons/armor). The rest is up to you to fill in and decide what it represents.)