Using Essence's that don't specify level

At what level is it best to use the Screaming Essence of Greed on Armor?

I think the wiki will show what level requirement the mod from that essence would be. But the item level on the item is what will dictate all the other mods. The only issue you might encounter with such a thing is if you are using it on a low level item, the essence mod might make the required level to use higher than your character so you wouldn’t be able to equip it right away.