Subscription is a special type of purchase. Once you've signed up, you can collect 300 gold coins every day in the same menu where you had done so in the first place.

Should you skip a few days and not collect your gold, you will still receive the entire accumulated total pending upon the next time you log in to the game.

Subscription is purchased for 30 days and is automatically renewed as soon as this period runs out. You can cancel your subscription any time you want on the corresponding page of your application store (the App Store or the Google Play).

iOS: https://support.apple.com/en-us/HT202039

Android: https://support.google.com/googleplay/answer/7018481?co=GENIE.Platform%3DAndroid&hl=en