You can buy Gold Bars from the in-game shop. Just click on the green '+' symbol, next to the Gold Bar image at the top of the screen and you'll be able to make your choice of Gold Bar bundles from the store.
You'll be taken through the steps to complete your purchase, using the details saved in the App Store account held on your device.
Once you have Gold Bars in your bank, you can use these to buy in-game items like boosters or extra moves. Tap the booster you need and you'll be shown the cost in Gold Bars.
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