It's a lot more forgiving than I make it sound, getting disease usually just means your stats go up less. Just for the love of god don't leave it all to Tauemon, he's wise beyond his years but he is not good at executing on that knowledge. I recommend holding off on looking up an optimal rice farming guide until you're to the point where you can't progress at all anymore, which for me was before the final boss.

Also, there's an easy difficulty for both farming and combat individually (and that you can select at any time), so if you'd rather focus on one or the other you can!