I had DSLR photography experience, and before that I had Canon point-and-shoot experience – but nothing else!
When it comes to cinematography, I think I was helped a lot by the fact that I had been shooting stills as a hobby (focused on food, dogs, cats, and friends) and always used manual focus with a fixed prime lens (usually a 35mm). So I had to develop this mindfulness of space and composition and reflexes around the focus, which I think is harder to develop if you’re used to shooting on auto. So that’s one great way to build up cinema skills without paying all the costs of shooting in motion.
When it comes to editing, I think the secret to video editing is that it’s just an extension of any other kind of narrative edit. So if you have experience with scripted film edits, written script edits, editing your own blog posts, editing a friend’s grad school application personal essay, editing policy documents and company e-mails at work… you are still building your skills as an editor. Anytime you take a story and apply decisions reg. the format and the audience it’s for, you are an editor. It’s easy to miss that, and consequently miss a chance to become better at what you really want to do.