In skyrim where can I buy all kinds of soul gems besides whiteruns Mage?

[*] Go through Dwemer Ruins. Destroy the mechanicals, as most of them contain Soul Gems. Plus, you can pick up the metal to smelter into ingots to use or sell.

[*] General Merchant vendors sell limited amounts of gems.

[*] Almost every Mage sells them, Check out the College of Mages.

Other jarls have court mages, too, not just Balgruuf in Whiterun. There's Wylandriah in Riften, Calcelmo in Markarth, Madena in Dawnstar, etc. There's also Falion in Morthal and a bunch of mage merchants in the College of Winterhold (and if you join the college, you can take free soul gems from the second floor of the Hall of Countenance). Regular merchants like Belethor in Whiterun or Sayma in Solitude will have them, too, full and empty.

Though the mage vendor in every hold is the best place to get filled or unfilled soul gems, also check the general goods vendor. They may not have as much as the latter, but they will have some. Also check the shop in Riverwood, I've seen those guys sell a few.

All the other mage vendors, as well as the general vendors, can also sell soul gems.

I recommend hitting the Mage College, as there are several mage vendors there.