Perhaps the best place to start with such a prolific artist, The History of Eric Clapton, from 1972 on Atco SD 2-803.  Covering music from the Yardbirds, Bluesbreakers, Cream, Blind Faith, with Delaney & Bonnie, Derek & The Dominos as well as solo recordings; this is a great intro to Clapton's early musical career.  With around 100 albums in Clapton's repertoire, it would be expensive to have them all, so this may be a good start! With the Yardbirds here is I Ain't Got You:

Eric Clapton's Rainbow Concert, was organised by Pete Townsend, a friend of Clapton's, partly as a way to get Eric working again after a 2 year musical slump and way too much heroin use.  The concert was a success and a start to recovery for Clapton.  I don't think there was an awful lot of rehearsing before this concert, as is evident in the songs! But a good album none the less. Playing with Clapton is Pete Townsend, Ronnie Wood, Rick Grech, Steve Winwood, Jim Capaldi, Jimmy Karstein & Rebop. On RSO label, 2394-116 here is their cover of J.J. Cale's After Midnight:

The fifth solo album by Eric Clapton, Slowhand, is the favourite in my collection of Clapton's solo work.  On RSO RS 1-3030 from 1977, this album has three huge hits in Cocaine, Wonderful Tonight, Lay Down Sally and my picks from this great album  We're All The Way  and the bluesy  Mean Old Frisco:

Recorded on tour at the Budokan Theater in Tokyo in late 1979, Just One Night is a superb double live album.  If you like live albums this is the one to get of Clapton's. The band is awesome, the sound is good and the music selection is also great.  On RSO RS 2-4003 from 1980
here is the Otis Rush song Double Trouble:

Behind the Sun, from 1985 is Clapton's 9th solo album, and second on his Duck Label, distributed by Warner Bros.  Produced by Phil Collins, this album is very well done musically, but I feel it is missing something...passion perhaps.  Kind of feels like he is just going through the motions, not really into the music.  Listen to Knock on Wood and see what you think.

Eric Clapton's 11th solo studio release, Journey Man from 1989, was a far better album than his last few.  On his Duck Label, 92 60741, but now distributed by Reprise records, this is a return to the Clapton I admire, and I feel his best record since Slowhand.  Pretending, Bad Love, Before You Accuse Me...lots of great songs, but my pick is the song he wrote and performed with blues artist Robert Cray, Old Love: awesome guitar work on this song.