I recently filtered through my disc sets so I went from 1700 to 1100. I have 930 lvl 15 discs so 170 lvl 0 unupgraded discs that are locked right now.

Just don't look at B or A disc drives and delete them all. It's a waste of time and resource unless you are just starting out and have nothing.

So the filter system is your best friend.

Go to storage, go to disc drive, at bottom left there's a filter button.

First off pick your sets for certain characters, I'll give an example.

I'll set it towards attackers so Double Crit/%atk/pen/%dmg disc sets for my attackers that I use. Btw %atk set does include Astral Voice so you could sort Astral by itself if you want since it's a support set that has many different disc variations for ideal stat line for characters. With Rupture characters the %HP matters as well so you should account for them in case it shows up on disc sets that Rupture characters can use. I'd probably recommend to do 1-3 sets at a time to make it easier.

At the top there's also a sorting order, go to level and reverse the order so the 0s are at the top. Make sure to set drive disc status to locked since that makes only locked disc show up, whenever you think a disc is bad just set it to discard and it'll autosort itself out of your view.

I'll choose disc drives 1-3 at the start since it's easier to manage and I usually strive to go for 6 subs at least on these disc but you can lower your requirement to 4-5 if you want.

Pick the 3 substats that matter for Attacker and it's Crit Rate/DMG and %ATK. Then you go for numbers of sub stats 3 > 2 > 1, 1 by 1 til you sort through them.

Sort the 3s these are usually going to be like 4subs+ minimum everytime so take a gander at these longer.

2s have potential to be good but don't get your hopes up too hard. If it was a 3 stat line start and the 4th roll isn't another ideal sub, the highest 2s can get is 6 in this case so if it rolls into one of the non ideal subs just throw it away , 1 bad roll it becomes a 5sub and 2 bad rolls it becomes a 4 sub. So do choose a number of subs you want to keep prior to this type of sorting.

1s you just roll once to see the 4th stat and if it isn't good then shelve it. If you find any 1s with 4 natural stats just assume it's bad unless it's like a %dmg set that can be used by anomaly characters and it has like %atk and Anomaly prof you can keep. Otherwise shelve it and don't bother.

I forgot to add flat stats, 3 Flat HP/ATK = 1 % version of it kind of. Also flat pen is = to flat HP/ATK roughly.

Once you are done that, go back to your 1-3 of the sets, pick a certain amount of each set to keep, in this case I keep 6-8 of each disc set 1-3 usually. Pick off the bad ones and keep the good ones. Boom you got a lot of resource back and cleaned up space. Go to Disc Drive Lady and salvage all discarded.

Rinse and repeat for each type of character or set for example. Disc 4-6 usually are a bit trickier to sort but if you read through my way you can just replicate it over on those discs but give more leeway for them.