Echoes is a possibility...though I suggest starting with a full album, because it's probably a good idea to get a taste of Pink Floyd's concept-album style. I'd suggest either Dark Side of the Moon or Wish You Were Here. Dark Side of the Moon is very universal. Wish You Were Here allows you to see what a longer suite sounds like. Both should be among your first purchases, I think, and I would follow them with Meddle.

My two cents, anyway...

__________________
"And with these words I can see
Clear through the clouds that covered me
Just give it time then speak my name
Now we can hear ourselves again..."

WrightSatellite #1