Warning: This will result non-targeted ads (the old fashion way :), no YouTube / Google search history, YouTube not highlighting which videos you've watched, YouTube not showing your watch progress on a video, and Google Maps GPS history to name a few. Proceed at your own discernment.
Personally, I got rid of everything except my YouTube comments and live chat history and switched my email to Tutanota's free, encrypted, open-source email service. I use my Google account for everything else other than email. :)
Pause all your Google Activity page. Tap all buttons on the right to turn off ("pause").