It’s important to know precisely what you’re buying. Real money can buy you in-game currency, which you can use to spend on all sorts of things including food, potions, crafting materials, armor, and all sorts of other resources.
These are all designed to give you an advantage in the game.
Be wary of the games exchange rate, because you may not have enough to purchase what you need.
Take advantage of in-game offers and deals, and be sure that you’re getting the most bang for your buck.