To answer the Coin Case, I think you could make an item named "Crystal Pouch" or something, and make a variable that counts the crystals. Then link the item to a common event that would call a message text.
And when you use the pouch, a text message appears telling you how many crystals you have collected. By letting the message box call the variable like this.
You currently have \v[*Variable number*] Crystals.