I've seen a lot of great stuff on Mastodon but when it starts to become overwhelmingly political, I dip out. Problem is that you have to follow an abrasive amount of random people to start seeing anything across their fediverse. Shit in the beginning, awesome/hits the mark at least in terms of twitter replacement - after you follow enough people.
You're right, I do need to build up my watch list. I'm just not sure where to start. I'll probably have to parasitize the watch lists of the few people I'm already watching.
Hashtags are also a good place to start! For example, if you're looking for science content you can follow the #science hashtag. Once you have those posts coming in to your feed, start following the people and hashtags you're seeing on the posts you like best. It'll start snowballing from there.
Also, don't worry too much about following too much at first. Get that feed populated, then pare it down later. Filtering is pretty powerful too, so a lot of times you can get the good parts of a hashtag and filter out the bad parts instead of the all-or-nothing following of some social media.