My preferred way to browse here is using All and blocking communities I don't want to see. That way I get exposed to new things I wouldn't seek out on my own (for example: British archaeology)
I accidentally blocked a community while trying to block a user and when I went to unblock it, I saw I had 1250 communities filtered. If I had to guess, 90% are either porn, sports, or anime.
A crap ton of them - too many to count quickly. My intent was to sort by subscribed, but we're still getting a lot of new communities, so I mostly sort by new, and block communities I have no interest in or that spam a lot. The most common categories are gay porn, bot-generated content, and overly prolific meme communities.