So let me get this straight. You have do destroy a legendary with an aspect on it you might want just to get the materials needed to imprint another aspect you might want? Can’t decide whether this cat and mouse game is intriguingly fun or just annoying. Anyway I really wish Blizzard had come up with fun ways to farm for some of these crafting materials…
In reality you get like 20-50 legendary items for every apect worth extracting – so basically you should never run out of materials (as long as you do some helltides for souls aswell now and then)
Running out of gold is a total different thng however 
You’ll have plenty of mats. You’ll lack storage space if you try to save too much. You’ll likely hold stuff for changing out aspects, but at some point you’ll have to clean up.
Salvage asoects you have no interest in the aspect and the stats are not what you’re looking for.
Keep or extract aspects you want especially if they’re a high roll. You can use the legendary but if you want that aspect on a different piece of gear you’d want to extract it. (You could overwrite it too if it’s not what you were expecting… But once it’s imprinted it’s permanent).
When I leveled I started salvaging rares/legendaries and vendoring blues and below. Many upgrade mats I am maxed out on (not the more rare ones but veiled crystals, iron, rawhide… Even superior at this point). So, now I vendor more than I salvage.
You should have plenty of gold if you’re not enchanting every item and upgrading every slot for the most minor upgrade. (I had 272mil when I hit 100 but at the slower XP rate so it required more killing… Don’t know what would be a reasonable amount now).
intriguingly fun first few times, extremely annoying for the rest of the game.
The codex should contain all aspects. You should be able to override those min-rolls within the codex with what you find out in the world. Maybe allow the codex to store the top 3 rolls you find?
This along with the gem tab would likely clear up quite a bit of inventory space.
Quite a few of my tabs are extra aspects in case I find an upgrade and/or some high rolls of aspects I don’t need for my build on the off-chance I want to try a new build.
Not only that, at higher levels you need to salvage 6 or more legendaries to get the materials to imprint 1 aspect