I like Sagiri, Elf and Tomoe, and wouldn't mind one of those three winning at the end (although I'd say is 90% probable that Sagiri will win), Yamada Elf is definitely best girl, every time she has screen time the anime gets interesting.
Elf. I don't mind Megumin either.
I love almost all their designs though. Maybe it's just my adoration for Kanzaki Hiro's art, but I love the way he designs characters. I hated Kirino from Oreimo so I'd take any Eromanga girl over that whiny little bitch, any day.
Sagiri is at her best when she acts like a perv, but that's not too often. Megumi is the cutest looking girl IMO, but she hasn't gotten a lot of time to shine and seems to be outside of the harem. Elf wins by default. At first I thought she talked too much and was annoying, but I've been warming up to her as of Episode 8.