Thanks for your feedbacks! Game balance and explanation surely is something that is missing right now, I’ll explain some of the points here in case you want to try it again:
- You can only upgrade “elemental” cows, so cows that got a potion once, the base cow doesn’t do anything when milked
- For potions you can open your quest journal with Q, doing quests grants you specific potions
- For the cows issue some of them indeed are less useful than the others, not much to say on that part