Last few albums I bought were the Steely Dan ones, Pink Floyd DSOM, Animals and Meddle (have had Wish you were here for a few years!), Future Sound of London, Aphex Twin, Fleetwood Mac Rumours Re-mastered, Bob Marley Legend, Belle and Sebastian, loads of classical (I mainly like the impressionists such as Debussy and de Falla and ballet stuff like Tchaikovsky).
Id personally recommend going backwards in time rather than forwards with Floyd, the 1st three albums are IMHO the best, though a different thing. Piper at the Gates of Dawn is one of the best psychedelic albums ever and Saucerful of Secrets, More and the live part of Ummagumma represent excellent UK space-rock.
As for FSOL ensure you have Lifeforms, it is IMHO their landmark album followed at some distance by ISDN. The Papua New Guinea 12 is obviously essential too. Aphex Twins Selected Ambient Works 85-92 remains my favourite, though all his output is worth a listen. Warp label-mates Black Dog Productions and their later off-shoot Plaid are simply wonderful, as are most Warp acts may be worth trying one of the Warp anniversary compilations to get a handle on this superb label.
To track the influences of FSOL, Aphex Twin etc back to their roots look as ever to Germany, early Tangerine Dream represents the exact crossover point for electronica from its roots in abstract modern classical (Stokhausen, Cage, Subotnik etc) to a more wide and commercial field. The TD albums to start with if you are coming from the Aphex Twin direction are Alpha Centauri, Zeit and Phaedra they effectively invented ambient house, but get little credit for it! Avoid their later stuff (i.e. post Rubycon), it all went horribly wrong IMHO.
As for reggae Id recommend jumping head first into 1970s and early 80s dub, look out for anything by The Scientist, Prince Jammy, King Tubby, Lee Perry etc recorded before about 1982.
If you like Belle and Sebastian you have to try Nick Drake he only made three albums, Five Leaves Left, Bryter Layter, and Pink Moon. All are essential, and definitely get these prior to any of the posthumous compilations of out-takes etc.
Neu probably Neu 75 but all are great (Im surprised Tony L hasnt already recommended this along with Yeti)
Amon Düül IIs Yeti is quite obviously the best rock album ever made, but it is hard to recommend as I still dont know which (if any) of the current CDs are legitimate, and whilst I
know Im right it is a bit much to expect people to splash out 40-70 quid on a original vinyl copy! Worth trying some Can or Faust though as both are well reissued. Start at the beginning and work forwards with both.
Tony.