I need to make a topsy turvy cake to feed 50. Can someone tell me what size pans to use? I am thinking I will do their layers for each tier and carve them. TIA

There's not much waste in a topsy turvy if you just do the "cut on an angle & invert" method.  If you taper the sides, you lose a little.  10, 8, 6 will give you 62 party servings to start with.