youtube is a great, try to watch videos made in the last year as they will have the newest and most recent updates. Also, you are kinda vague when you say digital marketing. Find something you want to do and then try to do it for as cheap as possible for practice and experience. I started and made a WordPress site for less than 20$ a year. Instagram accounts are free so you can try to build a “brand” page of some kind.
I went to a local extension college for an adult education program and highly recommend it. I can’t imagine getting the same quality and quantity of knowledge from YouTube or so. My teachers knew exactly what kind of skills the industry requires, and where to put emphasis