Best focus for music business development

As a new producer/creator and working during my spare time on it, I initially wanted to solely focus on development of my skills and tool set. Actually, that alone takes quite a pile of time and continuous investment.

But, in addition, I am being advised by various Youtubers to spend an equal amount of time on marketing and sales. A (small?) selection of services and platforms to set up reads like this:

Dedicated website, Twitter, Facebook, Instagram, Youtube, SoundCloud. In addition, one must go through a distributor like CD Baby or Distrokid to publish on streaming services, with another race towards playlistings.

So, I am curious: What should aspiring producers focus on? What are some experiences of yours?