I don't have this release, but it would seem to be a fantastic place to start:
http://www.amazon.com/Piper-at-Gates...s_all_3#disc_3
I would echo Mortte Jousimo, but stop at Dark Side. Actually Atom Heart Mother wasn't that good IMOHO. Pink Floyd Live At Pompeii is one of the greatest concert films ever, except the directors cut sucks, original release is a bonus on the DVD and the one I stick to. I got a bootleg LP compilation of all the early singles from the Syd and early Gilmour eras misleadingly titled "The Best of Pink Floyd", it seems to be the most comprehensive collection of that era's singles.