A few questions

I’m having some trouble here identifying what legendaries are sets, which ones go together, which ones are worth selling and how the synergy works between items.
Also I have a level one rogue with its level one normal cap. I have in her stash a lvl 91 epic that’s pretty amazing but it doesn’t show that it increases dps… In fact it’s minus 3.3 dps… How can that be?

Anyone willing to help me figure out all these items.
I play a wizard and warrior now and I have 40ish legendaries and I can’t tell what to do with them all and why some dps goes up or down depending on what epic or legendary I am wearing.
Thank you

screenshot that minus thing. i dont really understand that part.

Now it says 2.4 plus… I’ve been getting a lot of bugs. Not sure what’s going on.

Anyway, is there a link you can give me to show me what legendaries go with what ones? I see some have the same green attribute but aside from that have no idea what’s best. Here is a pic of my current gear on my wizard.

And some random legendaries in my stash

Thanks for the help and response.