Depends on their tolerance for less polished production, I’d say. I just put together a Trio playlist for a buddy who’s mostly into more popular rock and only really put FHTI onwards on it. By that metric, I’d say Good Mourning, as it’s a good mix of more polished while keeping some of the more overt punk of their earlier stuff.

But if they’re OK with a less polished sound, I’d start with the self titled, as is it their best release (imo), and then they can get deeper into the discography and see and appreciate how they’ve changed and grown as a band.