It sounds like you're starting, so I'd say forcus on YOUR passion. You're going to be doing YouTube for years, it's not just a get rich quick thing.
1) Determine what your passion is
2) make good content on your passion (as brave saide)
but I would add 3) research your target audience. Know WHO you are targeting. Targeting anyone and everyone won't benefit you much. Know who your core audience is, research what they want, and make content to cater to what they want. That will make your content more watchable, meaning you'll get more watch time, and people will be more inclined to subscribe because they know what you create is in line with their passions.
I started wanting to just make art. Lots of people "just make art" so I decided to narrow down on drawing dinosaurs. The automatically attracts a range or audiences from teens, to parents who play videos for their kids. So that means I simply have to research what teens-parents are interested in the world of dinosaurs... they're interested in Spinosaurus... boom, instant content that draws people in and gains views.
Know who your target audience is, that alone will make targeting, and making good content that targets a specific audience a lot easier.