"For Alto" from 1968 is notable as Braxton's very first solo saxophone album, and the first ever(?) full-length solo sax album from any artist.
And it was a double LP, to boot! It makes a lot of "Greatest Discs of All Time" type lists, and is genuinely essential.
If you like the Art Ensemble of Chicago, "3 Compositions of New Jazz" (also 1968) is a gentle entry into Mr. Braxton's world.