Generally, it's not going to matter. We usually do them at the same time. However, that's a little tougher of a pace for the DIYer.
First Coat: Tape and one coat on the nails. As a DIYer, I would suggest that you apply your seam tapes first. That way, you are not going to be (wasting your time) coating nails that will end up getting coated by the tape and the tape's later skim coats.
Second Coat: Scrape down any ridges or lumps, coat the tape, apply coat on one side of corners, and coat the nails again.
Third Coat: Scrape down any ridges or lumps, finish coat the tape, apply coat onto the other side of corners, and coat the nails one last time.
Last: Use a bright halogen light ot go around and touch-up any leftover imperfections.