Most useful pot sizes?

[PaxTea]

I'm gearing up to do an order from repotme, because I haven't had much luck finding a local source for clear pots with good drainage. I went to rays first, but I'm not keen on the aircone pots because they look more frosted than clear.

The shipping for repotme is almost $10, so I am thinking that I should probably get extra pots, so that I don't find myself doing a second order any time soon.

I'll be getting a 2.75, 3, and 3.25 as options for the mini-phal.

I'll also be getting a 5.5 and a 6 as options for the new yellow phal.

Beyond that, what sizes am I likely to get heavy use out of? I think it's safe to assume that I will eventually own more than three orchids, although I am going to try to slow down and make myself wait until these three have lost their blooms...