This is a good question! So the first Genesis albums I knew were Abacab thru Invisible Touch because my family had those albums. The first actual album I bought myself was a tie between Selling England, Trick, and W&W, but I picked Trick because it was the first of the group I listened to. I bought them all on tape at the same time which was a lot of fun.
My first listen to A Trick of the Tail was extraordinary! When Los Endos faded out I was amazed at what I had just heard, an experience I don't know I've ever quite had in the same way with any other album I've ever listened to.
Funny thing about the Selling England tape was that the running order was different from the album and how I knew it to be for so many years. I think More Fool Me followed I Know What I Like, and I can't remember which came next between FOF and Epping Forest, but it was quite different when I heard the proper running order.
The cassette running order thing was quite common, I had SEBTP on cassette too, and it certainly was different, as was the Lamb, Silent Sorrow was on side one, effectively making it a disc one track. Other options for tape length balancing was editing tracks shorter (Justin Hayward's "Doin' time" on Songwriter) using extended versions ("Remember me, my friend" on Hayward/Lodge's Blue Jays was about 3 minutes longer, still the only stereo version on the track in that form available, despite 3 remaster/reissues of the album on CD, though it is on the quad version) or, bizarrely, including a song twice, once on each side! ("Winterwood" on Don McLean's American Pie)