I use NoScript, which is security software. As a side effect, it blocks most ads because most ads are served in an insecure way. It also lets you know how many different sources are set to run scripts from each page, which can be interesting. It's not uncommon for 1 page to result in scripts run from a couple of dozen sources, with other sources calling other sources, etc. It blocks cross-site scripting. I find it very useful. Some sites won't work with it, so I don't use them.
I use Pale Moon browser because it doesn't use telemetry and they're removing any telemetry code they find (it's based on FireFox, so there was quite a bit of it to begin with).
I use DuckDuckGo because it's a search engine that returns honest results, unlike Google which is a data gathering engine that also does searches and deliberately biases the results to feed you into an echo chamber.
Nothing major, just some very basic security and privacy stuff.
I allow ads if they're not blocked by NoScript for security reasons. Mainly YouTube. I'll accept being advertised to a reasonable extent at as the price I pay for content.