Arkcon has pointed you to the answer - typically, like dissolves like. This usually means that you need to alternate polar and non-polar liquids. If you simply poured them all together, all of the polar liquids would dissolve in each other, and all the non-polar ones would dissolve in each other, and you would only get two layers. So between two polar liquids of different densities, you need a non-polar liquid of an intermediate density.