I love your game man! I discovered it through a French streamer (like 3-4 days ago, on the first of January), wanted to try it out and then got addicted. I found all of the story mode secrets (of the old version perhaps? Didn't check if you added stuff) and probably also all characters that give you an item (or card). 
Almost done, phew
Maybe a small thing I'm abusing so just mentioning in case it's not intended: I use the "steroid" items on mons before they evolve so they have more effect and this boosted effect remains on the evolved mon. So i.e. rhydon gets +7 attack and keeps it when evolving to rhyperior, whereas using it on rhyperior would only result in +5.
P.S. I found (and owned) lots of rainbow mons, indeed newbs don't know their majestic existence like that one NPC says ;D
P.P.S Tell me if you want me to remove the image of all the story starter teams (kinda a spoiler?)