We calculate your own item level rounded up or down to numbers of fives.
for example 721 is rounded down to 720
726 is rounded up to 730.
You create a PUG for either a mythic dungeon or a normal/heroic/mythic raid. I acknowledge that each case is different. Lets assume you create a PUG for something you are interested in, appropriate to your own level. I didn't want to make multiple polls to cover every scenario.
The question is what item level difference do you ask from your group?