Don't be fooled by the advertisement, it's not a 3D game, but an isometric 2.5D with some 3D models here and there for the main character and monsters.
90% of it is gathering items to slowly convert them into other items to build and upgrade buildings. The monster you capture helps you in battles and to automate your base production, but it's not gonna make a change in the first couple of hours since all your quests revolve around base building.
This is a slow game, for people who love casual base builders is alright albeit a bit grindy. For those wanting a more battle/capture centric gameplay, you'll be disappointed by the first chapters of the game