I would like to buy lots and lots of Soul Gems. Petties etc.
It’s to train Enchanting.
I can’t find a reliable source that constantly has a good supply.
(Aside from Collette at the Mages College, and the Wizard in Dragons Reach, I can’t find anyone else?)
I’m surprised nobody else has said it yet but, BLACKREACH!
The area of the dwarven ruins Alfrand with the crazy giant glowing mushrooms. The main quest line brings you here to get the elder scroll.
There are a million dwarven machines that drop them, the falmer carry them sometimes, and finally, and the best part, you can mine them. Bring your pickaxe. Look for “Geode Veins.” I haven’t seen it mentioned anywhere else but a geode vein is where soul gems come from. You mine it like just like iron or ebony ore.
I suggest using a weapon enchanted with soul trap also because every falmer you kill will go right into filling an empty gem. When I got done I had about 60 or so filled soul gems and leveled from enchanting 50 to 100 with the one trip!
Do the quest to find 30 crimson ninroots while you’re at it and you’ll run into all the geode veins.