I'll 2nd the recommendation for K9. Very comprehensive in what it blocks, and at least when I used it, was free for personal use. Probably want to use adblockers, as it would have a tendency to alert (a barking sound) on totally legit websites (major news sites like foxnews and cnn) based on what ads were being displayed at the time!
Not sure if they have versions available for tablets, as I haven't used the product in a while, but it is worth checking out.