When I played the game for the first time, I also made similar mistakes. Now that I know the mechanics of the game I have H.POTIONx9, MINT TEAx9, CATBOOSTx9 in my backpack. I'm almost on the same stage of the game as you. I use spells sparingly because it is easier to recover HP than MP.
It is important to collect all the plants every day, you can not collect the mint leaves far in the forest because it is not worth it due to the fighting.