As trading rerolls IV, sorting by IV should be done bottom up,
or from the ends in for any appropriate GL or UL candidates:
That said, if you’ve got a 98% something and already have 6, you’ll likely never power it up so it’s viable as a trade candidate. My own trading stuff is sorted like this:
Anything useful I have enough of, regardless of IV.
Anything “desirable” that you don’t want to use so; shiny, legendary, regional, event, elite/legacy moves, rare and also high level (or at a good level for any PvP candidates) common but useful stuff because it helps others.
By the time I have, say, a good few of any trade candidates, so it doesn’t eat your storage, start transferring out the least desirable ones whether by low level or newest in terms of age.
Does that make sense?