let's see. i distinctively remember going to the record store and spending 30 minutes deciding which one to get. technically, i bought the dance first (or my friend did for my birthday), but as far as a studio album, i bought rumours. not because i knew of its magnitude, or because of the declining relationships rumours was about, but because i recognized more songs on it
i knew NOTHING about fleetwood mac at the time. i just knew i was going to eventually own all the albums they ever released. so the second was probably the white album, then mirage, i believe. tusk, then tango. i think i bought tango used, and it hurt me because it was one of those albums i really didn't want, but was only buying to complete my collection. i never bought a new copy and i think a few songs skip
and of course i bought SYW on release date.
(i'd like to add that i went on to buy mystery to me, heroes are hard to find, bare trees, and behind the mask but this is the rumours forum and i really don't know which order these came in other that M2M first)