From what I've read, everyone gets all 3 starter families, plus Audino, Scraggy, Minccino, Emolga, Foongus, Axew and Hydriegon.
Also, if you happen across Victini's, Cobalion's, Terakion's, Virizion's, Reshiram's or Zekrom's AR code, you unlock them automatically. Everyone else you need to get...