To disable: Settings > Privacy > Advertising > Limit Ad Tracking
You can also disable Location-Based Ads: Settings > Privacy > Location Services > System Services (at the bottom) > Location-Based Apple Ads
Apple's ad tracking help doc: https://support.apple.com/en-us/HT205223 (Apparently they derive your gender based on your first name or the salutation on your iTunes account)
Remember to check that setting after each update, it often gets disabled after an update. I've pointed this out to Apple multiple times and its often fixed for a few releases until their fix regresses and the bug returns.
You can also disable Location-Based Ads: Settings > Privacy > Location Services > System Services (at the bottom) > Location-Based Apple Ads
Apple's ad tracking help doc: https://support.apple.com/en-us/HT205223 (Apparently they derive your gender based on your first name or the salutation on your iTunes account)