I run a Dragon Emblem team myself, and I feel like +Spd is the way to go. I generally consider 3 Spd to be way more valuable than 2 Atk, and probably better than 4 Def or Res. My Nowi is sitting at 45 Spd as we speak, and it's really nice how basically no one can double her (especially with Ninian support boosting her to 51 Spd). Although admittedly Adult Tiki is slow enough that you probably shouldn't bother with +Spd on her, and if I were you I'd probably instead run +Res to patch up that weak point. If you aren't interested in running +Spd for Fae, I'd run +Def on her for the exact same reasons (I'm strongly considering that for my own Fae, even). I'd only really recommend +Atk if you have QR on Nowi or something, because otherwise she's in a Spd threshold where every little bit can save her from a lot of doubles.
Do keep in mind this is all subjective and is probably biased by the natures my manaketes happen to have.