A rather boring thing is that you have to complete the whole first chapter before unlocking gacha. The infinite reroll gacha gives a UR adventurer, plus a chance of another drop of UR adventurer/support/card. After that, you'll get free 15 gacha tickets and generously ~6k gems.
The combat system is okay-ish, but the mobile control is horrible for me. No camera lock-on and the accidental dash is annoying, probably because of the swipe gesture. Playing on the PC port could give better action combat experience. The controller support is great tho.
(will possibly update once I make enough progress.)