A very easy, effective, multi-layer setup:
1. Browser adblocker
2. Pi hole running locally
3. Pi hole at your home network router level
And 4, not as easy but effective, a firewall like Little Snitch
Edit: the other good news is your old data loses value quickly, so starting today is still very effective: you haven’t missed the boat yet!
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1. Adblocking via private DNS (e.g. https://mullvad.net/en/help/dns-over-https-and-dns-over-tls)
2. Prefer websites over native apps wherever possible
3. Browser adblocker
Hosts file adblocking is also possible on a phone where you have root.