first of all: D2:R Discussion sub forum:
https://forums.d2jsp.org/forum.php?f=148 
now, I won't talk much 'cause idk how things are going in d2r, but I'd say that as long as you have space, you can keep w/e you think it's worth keeping.
I personally collect and keep low runes and p gems. (in D2) people buy sets of 40x p gems or more etc, so if you can have a mule full of p gems that is a start. And the same with low runes (but ofc that's up to you).
sigon set, and angelic rings and ammy are often searched, so keep/collect them. Other pieces of set like irathas, deaths, sanders and cleglaws are less looked for, but now the important thing to consider is, the price... check how much some items are worth and then you will know which ones to keep and which ones not.
and regarding your uniques... I think only gull and demon limb are the ones I've seen people looking for (not that much ofc) but again... IN D2...
you have to bare in mind that almost any item in the game can be worth something for a player that is trying a weird odd build. The question again is: is it worth to keep an item just in case? knowing that if finally someone looks for it s/he will offer less than 10fg...? when I could use that space to keep other things...
finally, check the iso/sell forums regularly and there you will know which items are being sold/bought and if you have any of them that is worth a decent amount of fg... you know that item is good to keep.
good luck with sell
This post was edited by Necromorfo on Nov 27 2021 03:39pm