A place where I might actually be of help. Big Gabriel fan, so:
'So' is his 5th solo album, and generally considered his best.
1 (usually referred to as 'Car') is, IMO, his worst, although it has two great songs 'Solsbury Hill' and 'Here Comes Flood'.
2 (usually referred to as 'Scratch') is a step up, but a bit hit and miss.
3 (usually referred to as 'Melt') is where he hits his stride. Absolutely brilliant from start to finish. It has the song 'Biko' that Rusco mentioned. It's also his dive into world music.
4 (usually referred to as 'Security' because Geffen in the US got tired of him not giving titles to his albums and forced him to come up with something). Very tribal sounds on this one.
'So' is next and you already know about that one.
'Us' is another classic; Chuck full of goodness.
'Up' is his last proper solo album.
He's done 3 soundtracks and 'Passion' is the soundtrack to 'Last Temptation of Christ' and it is great, but he more or less curated that album and didn't really compose it. He started a world music label/recording studio (RealWorld Records) and has a ton of great world music releases. Passion is sourced from sounds of the Middle East and northern Africa.
Hit is a definitely a great place to start (you'll get all the hits and the second disk is called Miss which are singles that didn't quite make it in the world).
Another option is to get New Blood which is him re-recording his songs accompanied by an orchestral score, which I really like. His voice has changed over the years, but it's still got that sound that I love.
He's also done a covers (song swap) album, but we won't talk about that.
Hope he does something for you.