I buy from a range of vendors all over the world. Much of what I enjoy is interesting jazz from the period right after the ’60s. There developed more spoken word (Gil Scott-Heron), soul jazz (The Visitors- a/k/a the Grubbs outta Philly) and so-called spiritual jazz. I buy mostly used records because many of these have not been reissued and/or I prefer an earlier pressing.
There is an initial huge learning curve, both in terms of fluency of the works of a given performer or composer, but then being exposed to different performances, some by the same artist, at different times. Layer on layer of knowledge if that intrigues you.
To me, the quest is always for more, interesting music that sounds good. I have lots of notable or rare pressings, but the quest is always for new to me things.
In terms of how best to buy, that’s a whole other subject.....