Apple themselves recommended Ghostery Lite. I feel like that one had some trouble in the past but I can't recall why. Regardless, I installed it and Magic Lasso to see how they do. I used to use Wipr with some success but it appears to be no longer free. Still, if Ghostery Lite and Magic Lasso don't work out, I'll pony up for Wipr.

I gave Ghostery Lite and Ka-Block! a shot and they blocked ads on most sites except for reddit. Pretty good for free.

Wipr blocks the same ads as the above combo, but also blocks those on reddit.

YMMY