Note that Ghostery will block trackers but they do sell your usage data themselves.

Use privacy badger or a tracker-blocking list for your ad blocker if you're that concerned about privacy.

On another note, as an ad person, context-aware ads are alive and well, for instance if you mention a specific thing in your Facebook updates you're more likely to see an ad for it. But the hard fact is that personalisation and retargeting works very, very well.

The real mistake ad companies do is that you should not see that ad if you didn't want to buy the jeans (or you bought them on a different device), which is hard to guess but not impossible