Things I’ve turned off in iOS

Ad Tracking

Settings > Privacy > Advertising > Limit Ad Tracking (turn it on)

Location-Based iAds

Settings > Privacy > Location Services > System Services > Location-Based iAds

Apple Music

Settings > Music > Show Apple Music

Predictive Text

Settings > General > Keyboard > Predictive

Lowercase keys on the keyboard

Settings > General > Accessibility > Keyboard > Show Lowercase Keys

Siri suggestions

Settings > General > Spotlight Search > Siri Suggestions

Frequently Visited Sites in Safari

Settings > Safari > Frequently Visited Sites

Battery Percentage

Settings > Battery > Battery Percentage

Almost all notifications

Settings > Notifications

Background App Refresh for almost all apps

Settings > General > Background App Refresh