Game launched for Android an iOS a little over a week back, though currently region locked to NA if you're elsewhere.
It's probably been one of the more generous gacha games I've played in a while and there's definitely lots to do early on. Some typos and formatting issues here and there, as well as tutorials standing to be a bit more informative, but overall it's not hard to figure things out.
If planning to reroll, I'd also highly encourage doing it through an emulator, as one can delete a specific file that way instead of having to reinstall on a mobile device. Process will like vary per device, so consult your local google for how-to. The goal should be a good 4* combat unit or two like Ottarl, Argonaut Bell, or Ais, but the current step up banner has a good Ais variant that makes targeting her a waste of resources since you'll probably snag her in the step-ups and can't use same-name characters in PvE stuff. The 4* Lefiya is a pretty solid caster, too. Dupe pulls go toward a limit breaking resource, so it's possible to pull 3 or 4 of those two units for 2200 currency, which again likes to flow between various early missions and S ranking stuff.
If you pick up the game, my friend code is 1526356355. Currently have the Sparkly Ais set and she can carry for support for a good while early on. Though in general, I'd say progress through Bell's story until you have trouble S-ranking, at which point you can divert attention to the events or material farming to rank up units. You're also going to want a healer eventually, which I've been using the 3* Riveria due to what RNG has given me, but there are a couple better options.