Pete -

To my knowledge, the single disc movies are NOT repeated in the sets (I have the first twelve boxes). There's a two-disc set called "The Essentials" which includes two MST3K Classics, "Santa Claus Conquers the Martians" and "Manos: Hands of Fate." Both of these are great. I'd start there.

As for the boxes, the consist of four movies each, no particular order. There seem to be more with Mike Nelson than with Joel, though.