Using Google Play Games turn-based/multiplayer features, you can challenge your friends or even random players to head to head matches and then watch the results instantly.
To challenge another player to a race;
The other player will then receive an invite to race as a notification, as long their notification settings permit it. Once the user accepts a match invitation, the user is joined to the match as a participant.
If you select “random”, a notification that the match is underway will be sent once another player joins.
To add friends on the Google Play Games you must activate multiplayer mode and use your Google+ account to connect with your Circles. You can play friends in real-time and turn-based matches, invite people from your Google+ circles or play with people who are near you. First, connect your game to Google Play by tapping the button in the Settings menu. This will connect your current Google+ profile to the game. Once the game is connected, Google+ friends who play your games will appear in your friends list.
Both players must have one another in their Circles to see each other in-game
To edit general settings, notification settings and to view muted games:
Note: To turn off all Play Games notifications, you can untick the boxes next to all notification options.
With select multiplayer games on Play Games, you can easily start playing with people nearby by turning on the ‘Nearby players’ option. When people near you also have the game open and the option on, they can join the game instantly.
Learn how the Nearby players feature detects people around you (usually within 300 feet).
Nearby players will turn off every time you exit the game or the multiplayer section within a game; you’ll need to turn it on again to start another game. Turning Nearby players on or off within a game will not change the Nearby setting of your Android device.