I'm going to have to suggest Dawnforge. It's got only a few class changes from the core rules, and it provides
many more options, but you don't have to use many of them if you don't want to. It's a fascinating world, an excellent product, and--perhaps most importantly--you only need the single campaign book to play. (Well, plus the three core rules books, of course.) Suppelements exist, but they aren't essential.
Much as I love Scarred Lands, I have to admit that it's harder to get started in that setting, because it's not as self-contained, in terms of number of books, as Dawnforge. If you're willing to buy a handful of books, you can't do much better than SL, but for someone just starting out, Dawnforge is of equal quality, and easier to get into.
(I'm tempted to suggest Ravenloft, since it's not a WotC setting
anymore, but I think that would violate the spirit of the request, so I'll refrain.

)
If you can wait a few months to start, you might also give Egyptian Adventures: Hamunaptra from Green Ronin a look-see.
