Go to the Google Play Store, search for "Google Opinion Rewards" & download it. Make sure notifications is "On". Google sends surveys for you to take. They're usually only a couple of questions & you usually only get 10¢ for the short ones. But, it happens once (?), or twice (?) a week. It actually adds up fairly quickly. Then, when you want to buy gold, or a booster, or whatever, it automatically is the 1st option for "payment" type. And, you can use however much you have & add a credit card or PayPal or whatever to pay the remainder.
Of course, it goes without saying, you can only do this with an Android phone. I don't know if Apple has something similar.
I think it's neater than cutting butter with a hot knife 🔪!