Completely stopping tracking for shopping especially is gonna be impossible, but since you say “least trackable” I think there is some obfuscation you can do. Keep in mind, I’m by no means a security expert or anything, but general paranoia at the state of the internet has made me interested in trying to obfuscate my online identity for a while now (I say as I post on Social media…), so I’ve got some things I’ve found helpful

A simple easy thing is to start using browser containers for your different identities, which is built into Firefox. This way, details of one identity are less likely to leak into another, as in, what you search for in one identity isn’t gonna end up in the shopping results of another. Related to this, I’d look at script blockers and other extensions that can stop trackers. My go to is NoScript but I get some people don’t like it cause it’s fiddly and can break sites. I’ve heard good things about Ghostify but haven’t tried it myself. Getting started with NoScript way back, it was crazy to see how many different useless trackers and scripts were loading in the background that you don’t even see and are apparently completely unnecessary to the functioning of a site.

Then I’d also recommend using a VPN. I love it when I see ads being served to me from completely random countries because of how often I change my location, confirms that whatever advertising service that for whatever reason slipped by my blockers still don’t even know my general location.

And that’s about it off the top of my head. If I can think of more I’ll come back and edit my post.