Main Story Completed

I've finished the main story up to Kurobane's part, but now I have to do side stories and stuff? Puka Land? Is that like a FromSoftware game? There seems to be a lot more to do, so I don't know where to start lololol Anyway, I want to earn as many gacha stones as possible, so I want to tackle things that let me collect them first, but I have no idea what those are and I'm confused by how many elements and content there are lol The volleyball part seems to be mainly about earning 'Fangs', right? I need to research efficient 'Fang' farming routes for the bank robbery part too ✍️ Don't you think there are hardly any card keys? If you find the advanced area or something, you can go to where Mammon? is 🥹🥹 If you have any tips on what to do next or what's good to do, please let me know 🥹🙏