For me, with my android device, I like that I can turn off targeted marketing. I forget where the setting is, but google allows you to disable it. Turning it off makes all my google specific apps that have advertising show me a more random assortment of ads. Unfortunately, this setting doesn't apply to all apps as anything that isn't using googles advertising framework result in targeted ads.
With android app ads, 90-95% of the time, I am not even looking at my phone while the ad plays. It is a means to an end. USUALLY I load the ads to get a free thing in a game. There are also tricks you can do to remove ads in quite a few of the apps while still using them. Downside is you need to re-apply those tricks after each update and they don't always work. Scrabble is one where the tricks work great. That game has far too many ads... I shouldn't see an ad after every turn in a game.
I think the biggest challenge of removing targeted ads on a mobile device based on how much you want to pay for the device is that those are usually baked into the app itself, not into the phone.
I do prefer the random ads on websites to the email ads though. You buy a toilet on Amazon and the next few emails from Amazon are trying to help you with your new toilet collection.
The other ads I find creepy are when my wife looks a thing up on a site from her account on her device and a few days later I am getting ads from that site for things she looked up.
The above is all just my opinion on what you should do.
As with all advice you find on a random internet forum - you shouldn't blindly follow it. Always test on a test server to see if there is negative side effects before making changes to live!