Here's some tips as I see a lot are having troubles with the difficulty of this game.
-Buy low and sell high.
-Upgrades are really important, choose when and which ones to upgrade wisely.
-Consider playing with enemies off if it's your first time playing.
-If enemies are on, do not neglect to buy weapons you will need them!
-Use the hydro reset function if your having a hard time keeping up with bills!
-Chanterelle Mushrooms are immune to bug attacks.
-Rumors will often use nicknames instead of the displayed mushroom name.
-If you're going to purchase a mushrooms stock, it automatically sets you up with the maximum amount you can purchase and I'd suggest buying them all in most cases.
-Don't hold on to your stocks for too long hoping for that perfect sale, prices can plummet, or even worse, get infested with bugs or spoilage!