1. On your iPhone, iPad or iPod touch launch the official Facebook app and tap on the ‘More‘ button from the tab bar.
2. Now scroll down and tap on the ‘Settings‘ option. From the menu choose the ‘Account Settings‘ option.
3. Next tap on the ‘Apps‘ option.
4. From the menu and then on ‘Platform‘ option.
Finally under the ‘Game Invitations and App Notifications‘ select the ‘No‘ option.
That’s it. Now you will stop getting those annoying Facebook notifications from games and apps you don’t even use.