It is better to sell raw mats or refine then and sell the refined stuff + maybe some gold upgrade mat?
Selling end game refined mats (i.e. Ancient Spider Silk) + tempers (gold upgrade mat) will be more profitable. I'm not sure about profitability of refining mats other than end game mats but what I do know is that tempers will sell like hotcakes. So just because you can sell them easier, I'd still try and obtain the tempers as a way of making money. Stuff like refined iron won't really sell. I'd use them to craft training gear or vendor them.
Server - PC/NA
Vhevet - (S) Night Blade/Female/Orsimer
Ecaer - (M) Templar/Female/Breton
Captain Beaster Bunny - (S) Warden/Male/Red Guard
Ezaera - (M) Sorcerer/Female/Altmer
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What Can Go Wong - (S) Night Blade/Male/Bosmer
Izaer - (M) Templar/Male/Breton