There are energy timers, multiple types of currency, various tickets, cards to combine together, and ever elusive rare drops. Trust me, you've seen all this before.
But Square Enix was really pushing that this game was different and it had high production values so I stuck with it for about four or five hours. The graphics do look nice on the phone and there's actually somewhat of a unique story in here, but besides that I found everything else lackluster. The battle system is much more about what you have equipped than it is about any particular intelligence in battle. They actually have an auto-battle option that will always do the optimal thing for you, basically you just need to set up your character before hand.
And you know what the easiest way to set up your character is? Spend a bunch of money! You don't have to of course... but everything is gently pushing you that way.
After a handful of hours I had enough and uninstalled the app without ever paying for it.
I'm still holding out hope that someday Square Enix will release a unique Final Fantasy mobile game that is actually a full featured game. Something I can pay money for one time and then just play without constantly being pushed toward spending more.