1 and 3 are very lore-related, 2 has more like an "easter egg* feeling in respect to 1. I would play the three in order (in fact, that's what I did), but if you want to skip, skip 2 (or play it after 3). It's kind of the same situation as Silent Hill, where 1 and 3 are heavily related but 2 can be played apart.

And don't let them convince you that 2 is bad. It's not as mechanically good as the other two, but it's awesome in other ways (good lore, the best hub, power stancing, the best cat, the best fashion, etc.). Even as the worst Soulsborne is better than 80% of the games out there.