I paid for 1Blocker (https://apps.apple.com/us/app/1blocker-ad-blocker/id1365531024) since it runs locally on my phone to block ads as well as trackers from other installed Apps, whether on my home WiFi, other WiFi, or cellular data. There's a whitelist feature and the filtering can be tailored. I've been using it for years (before I got my current phone) so I can't comment on battery life but I've never noticed it to be bad.

It does break some apps if they're not whitelisted but that just gives me more reason to decide if I really need the app. It's also possible to temporarily disable the blocking (5 minutes, 30 minutes, etc) which helps with logging in (since so many login services involve trackers).