This thread helps a lot, being a new player I now have enough DM Crystals for either Saki or Spica and wasn't sure who to get first. Looks like I will be getting Spica but having not awakened any units yet and not having the materials to do so I think I will get Saki before getting and awakening fairies.

Seen Spica in a lot of guide videos too so she seems like the better choice, wouldn't want to miss her if they changed which units were up for grabs.