I'll give it a shot. I'm a pretty big fan, but if you wanted to get into Steve Earle on my terms, I think you could do it pretty well through these two records:
El Corazon is his 1997 album, coming after the material I'd use in a "collection" but demonstrating his range. Some rockabilly, some deeper pickin' and pluckin' country, a really good him/her duet, and one song (N.Y.C.) that from someone else might have been a one hit wonder candidate.
Definitive Collection - I actually listen more frequently to
another compilation, but I think that one was done behind his back by a jilted label, so I'll go this route instead. Basically stuff from his earlier career, rougher around the edges, and before his politics became potentially insufferable to many.
You get through each of those a few times, and you'll be a proper fan.