I got Loki after several spins. I wanted Ammy, but I'm lazy and reinstalling the game takes too much time.
Loki is a really popular mono-dark team leader and member, definitely a good starter.
I have been playing the Jap ver. of this addictive game for almost half a year. orz
By the way, although they give out free Magic Stones and have new bi-weekly dungeons all the time, it's probably not a good idea to not spend your stones for rolls unless there's a god fes or some special events going on (Like the current Community Appreciation event in Eng ver. or Muracore in Jap. ver), based on personal experience, unless you have god-like luck, the usual weekly Attribute-based events are useless.