Download the Google Opinion Rewards app. If you use an Android device, you can install the Google Opinion Rewards app from the Play Store. This app will send you the occasional marketing survey, and you'll be rewarded Google Play credit for completing them.
You can then spend this to get apps and free Play Store credit on games like Clash of Clans, 8 Ball Pool, Critical Ops . Most surveys only take a few seconds to complete, and award between $0.10 and $1.00.
Sign into the app with your Google account. If you aren't already signed in on your device with a Google account, you'll be prompted to sign in. Google accounts are free to create.
Enable location services on your Android device. You won't get many surveys unless you turn on location services. This is because many surveys are based on locations that you have recently visited.
Continue answering surveys until you've accumulated enough Play Store credit to purchase Gems. It may take a little while, but you'll likely amass a nice amount of Play Credit before you know it. Once you have enough to afford some Gems, open the Gem store in the game and buy a pack you can afford. Make sure your Google Play balance is selected as the payment method during the checkout process.
Tip : Open Twice A day to get regular surveys.