Ok, for tank circulation think powerheads, seio pumps, or my favorite Hydor Koralia pumps. The Koralis pumps give a very broad area of circulation and tons of flow for the dollar. That's where your 10 - 20 - 40 times circulation comes from.
For your skimmer, it's easy. Get a Mag 5. Your skimmer is probably intended for in the sump operation so water goes from the sump through the skimmer and back into the sump.
Your return pump is intended to move water from the sump back into the tank. Water will drain from the overflow into the sump at the same rate that the the return pump pushes it into the tank. Here is a head loss calculotor to help with your return pump selection;
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Having said all this let me finish by say in that if it were my tank, I'd use a Mag 5 for the skimmer, another Mag 5 for the return pump, and 2 Hydor Koralia pump #3s for circulation.
Hope this helps some.