Do you have advanced tooltips turned on? I would keep any high rolls for generic aspects that can be used across characters. Don’t keep low or medium rolls because you can just use the codex and it isn’t worth the space. Don’t use the high rolls unless it’s on an ancestral piece with decent stats, because unless you have duplicates you’ll probably replace it too quickly to be worth using anything but the codex. Obviously some aren’t in the codex so if you get a decent roll of those and it’s generic then it may be worth keeping duplicates.

As someone with multiple characters already it doesn’t seem worth it to keep class specific gear stored unless it’s for a build that you are specifically going to transition to, or it’s a perfect roll. Mainly store pieces for the build you’re planning for, whatever that is, and keep generic aspects in their own tab. I only store gems that drop at tier 4 (gem, flawless gem, royal gem) because you’ll need a lot of gems eventually but they’re not very important for the early game when leveling alts since tier 1 is so easy. You also shouldn’t be afraid to discard uniques. I’ve found them to be better to sell than salvage because they seem to just give the same legendary crafting materials but they sell for significantly more gold. There are a lot of bad unique that drop frequently and aren’t useful for many (any) builds. Don’t hoard them just because they’re shiny.

At least this is my system, keep what is important to you based on the space you currently have. Although I’m tight on storage I’m making it work.