You can use any size pots you want. I like the strawberry pot because the water comes out of the holes.
The pump sits on the bottom of the big basin. You put a large size pot upside down in the big bowl to cover the pump as you see it in the picture, then stack other pots as you like. Then you just run clear hose (Lowes) from the pump (also Lowes) up to the top saucer. You have to do a little cutting and drilling on the first pot that the pump is under. Cut out a little space on the edge of that pot so the electrical cord can run through and so that the pot can sit flat and also drill a few holes in the upper rim of that pot so water can flow inside to the pump. Since the pots already have holes in the bottom, you will only have to drill through the center of the saucers to run the hose up.
You have to use a masonry bit. They are a little expensive, but well worth it. You should get a bit large enough to drill a hole the same size as the holes in the pots. Then get a hose wide enough, but one that will easily slide through to the top. I got everything I needed at Lowes.
Put colored stones or rounded river stones (Lowes again) in the top and middle saucers for decoration. The stones will control how your water comes out of the top. Good luck. Have fun.