Smartphones are good at tracking everything you do on the smartphone and internet and you may not be able to stop all data from being traced on your smartphone but you can do a few things to help stop data from getting out and tracing you on your smartphone.
Use Incognito on your web browser
When using your browser on your smartphone be sure to use the browser in incognito mode which makes it hard for other websites to know information about you and your smartphone.
This also prevents ad companies knowing about your searches and what you're interested in.
Limit the App Logging
If you use apps on your smartphone check the settings in the apps and limit the logging of the apps so it won't log everything you do on your smartphone or through the apps.
Erase any old text messages
Erase any text messages that are no longer needed since it's possible for the internet to read your text messages on a smartphone to find out what you're interested in as well.
Erase any search history you have on your smartphone.
Since the internet likes to track your search history to show you relevant advertisements for stuff you may be interested in you should delete any search history that is on your smartphone.
The way to delete search history will depend on your smartphone so I can't give instructions on how to do so without knowing the make and model of your smartphone and whether it's an Iphone or Android phone.