The only real information we have regarding the set currently comes from Magic: The Gatherings head designer Mark Rosewater, who called it a tentpole booster release like that of Lord of the Rings: Tales Of Middle-earth
Every Disney Lorcana starter deck brings a solid array of cards and possibilities to the table, so picking up any of them won't prove to be a mistake, but Amber/Amethyst is generally the safest choice.
The former is a noncreature spell that still creates board presence
These persist much like item cards, and also often feature abilities or effects, however, they also have strength and willpower statistics
Its also interesting to note that Tifa itself can deal 7 combat damage due to melee if you attack each other player (Cadric, Soul Kindler plus myriad, anyone?)
Its a fantastic showcase for Lorcana in general, and really shows just how good the artwork is on these Disney-themed cards