YMMV says new users only (hopefully they allow everyone to participate)
From now until June 12, you'll get a $10 Google Play credit when you make 5 purchases with Google Pay on different days. Once you get started in the Google Pay app, you'll have 30 days to complete all your purchases.
1. Download Google Pay
2. Make 5 purchases (limit 1 per day)
3. Get a $10 Google Play credit
The Promotion is open for enrollment from 3/8/2018 at 12 midnight GMT to 5/14/2018 at 11:59PM GMT
To enroll in the promotion, you must install the Google Pay app (if you have not already done so), open the Google Pay app and opt into the campaign via the promotion screen during the Enrollment Period. You will see the promotion screen either after activating your first card or in the Live Feed. If you had previously downloaded the Android Pay app, please ensure that you have updated to the Google Pay app via the Play store.