pretty much this, and if you're short on items that could give you the ordo, just gather some wisp spawners from the thaumium altars, put some cursed earth underneath the spawners and kill the wisps, it'll produce quite alot of wispy essences of the primals, which you could smelt down to 2 aspects of the type of essence and 2 auramordo crystals from the crystalizer
True but i got 12 stacks silverwood from 1 forestOther options are Lead Ingots (3 mettalum, 1 ordo), Ordo mana beans (if you can find them and grow them at a reasonable rate), or chiseled Stone Bricks (1 ordo, 1 terra). Of these only the mana beans are pure. If you desperate for pure essentia, the essentia crystalliser is a godsend for that. I'd hesitate on using silverwood for essentia, as it's very useful for other things, and not easy to renew.