-
For an Android phone, it's difficult.
For web stuff, that's easy: Install the Firefox app, and you can add the extension for uBlock to enable ad-blocking.
For apps... it's very hard. Either you root the phone and install an outbound firewall to give you full control over web traffic and all permissions and phone access. Or you avoid root, but install a VPN and then choose a provider that gives you access over the DNS of the VPN, or run your own VPN.
To block adverts in apps is hard for novices, but blocking adverts on the web is easily achieved by changing your browser to Firefox.
My technique:
Then:
I configure uBlock Origin to pretty much strictly disallow all 3rd party stuff, except where it physically breaks a site (so on this site I allow Persona, but not much else).
This deals with 99.99% of adverts.
Then for my mobile, and to deal with in-app adverts, or adverts in web views (i.e. those adverts half-way down articles in the Guardian app):
That nukes 95% of in-app adverts and tracking.
I just don't see adverts on the web, and my web is fast and responsive. It's a real pleasure.