I sell all my mats.
I have all 4 large storage chests and I keep only the pieces with good traits... I should go through and decon more bad non meta sets though.
I don't need to sub to dump things into the craft bag because there are ESO+ free weeks all the time.
I have started just destroying trait mats or just never picking them up....
I do have issue with having 28 Rewards for the worthy loot chests right now though
I fill up my personal inventory, running PvE content and/or dungeons.
I do my crafting.
I vendor everything else I didn't need for crafting.
I store craft mats in the bank.
This usually gets me down to 10 items on my person, and I start all over again.
Now, I'm not into crafting everything...but it's simple and it works.
so my solution is not easy to do but if you have few friends then its the best solution i think.
so me and these friends (who no more plays the game) created this guild of 10 members and so now i have 500 bank space all for me, beacause none of them play anymore. and i use plugin roomba to auto stack all mats and never had problem with managing mats.