The shows that interest you. The ones you would actually watch.
I imagine this rules out kids shows for most adults. It sure does for me.
Also start reading books asap. I spent way too long watching dub+sub'ed Netflix in my target language. Wish I'd tried reading young-adult books sooner. If you're going to be pausing on every subtitle frame to read it, you might as well try books.
>> I imagine this rules out kids shows for most adults.
Not necessarily. Maybe if you understand everything, they become boring, but to me watching an interesting enough show where you understand 50%-80% of the dialog and try to understand the rest by context is kind of fun.
It depends on your level. I'm a big fan of Peppa Pig, because I think it's funny/entertaining enough for adults who understand >50% of what's being said. But before you reach that level, you need to watch something simpler. I'd suggest "Superbeginner" and "Beginner" videos in a YouTube channel called Dreaming Spanish