While theres not much strategy beyond team rosters and choosing which cards to level up, the slot machine battle system is fun, and I find myself playing it for longer periods than the other card battle apps on my phone.
IAP is there, of course, but Ive only bought 1 card pack out of curiosity & Ive done just fine playing through the first 12 "worlds" so far. I even got an EX Gomora (UR) card from using the crystals you earn by playing. IAP doesnt seem like a requirement to progress, and thats how it should be.
Geof7609 about Ultraman Galaxy