Your skimmer pump will need to be equivelant to the return pump. If the skimmer pump is too slow the sump will overflow and the skimmer tank will slowly run dry. If the skimmer pump is more than the return than the sump will run dry and the skimmer tank will overflow.
An easy fix would be to get a U tube from an overflow and start it as a siphon tube between the sump and skimmer tank to regulate the water flow. This will only work if the skimmer pump is smaller than the return pump so the siphon can have the draw needed.