He has one niche but very important use: he kills Elder Turtles during turtle times! He can speed up your turtle farming time considerably. See the linked turtle page for detailed guide. (Yes, he is a bit less useful now since turtles got HP nerfed in late 2016, but he still speeds things up).
He is really useful for new players (when you really want your turtles; later in the game you'll stop farming them, but until then...). Maxing his special is crucial. You may want to level up and evolve his unevolved copies just to finish him off (fortunately, they are pretty easy to level and evolve).
You probably don't need sockets on him, but since you'll end up socketing him sooner or later with some extra copies, uh, orbs, CDs, auto-heal...? Orbs are the only ones you really care, since it helps kill some turtles faster. And let's face it, he won't see any use outside turtle time.