Ok, dumping speed on Eldigan is the way to go so +atk and -spd is very good if not the best for him. For seliph, I personnaly would take 1000 feathers for him. He just has everything a bad unit wants. Unless you like him, you should probably pass as he needs a LOT of investment to be mediocre. If you lack red, you could build him for Arena assault for now but a very simple and cheap build.
I can't win. While summoning for Ayra, I got FOUR Eldigan's and a Seliph.
Seliph is +hp/-res and the two decent Eldigan's are +spd/-res and +atk/-spd.
Which Eldigan should I use and what set should I run on Seliph? I was thinking maybe Zanbato+ and Panic Ploy, but I'm not sure so some feedback would be appreciated!