Hello @Katty_Spitaels and welcome to our bubbly community! I have a perfect link here for you which explains all you need to know about how the piggy bank works, any questions, just shout me
You have to buy the piggy bank once it's full which I don't think is fair at all they are gold bars you've already earned and once the bank is full of you choose not to purchase it it stops collecting bars as well 🙁
Hey everyone @kalysta1 you have not actually earned any gold bars, I know its a little confusing the way they work it. You earn the chance to buy them at a highly reduced rate. Whether you choose to or not is up to you. They are not necessary to pass levels and so are classed as premium currency as they help you a little. Hence the cost because the game has to be paid for.
@vgambeta sometimes you can earn them in competitions. Have you checked out any of the communities contests? You can find them all here: