As I’ve said, most musicians agree musicianship as a whole requires a certain set of core skills. All of these skills are equally important, and the order of presentation here is not meant to imply that any one skill comes before another.
All the skills are primary skills and should be studied concurrently, not consecutively. These primary skills are mostly related to playing an instrument (voice is considered an instrument), singing (also for instrumentalists), being musically literate (reading and writing music), and playing or singing with others in a group.
Also, it’s important to develop a good sound, be accurate with notes and rhythm, learn to compose, improvise, arrange music for and direct ensembles, communicate with the audience, and to build a vast repertoire.
Of course, all of this takes some time. Becoming a master musician will take as much time as it takes to learn to be a Doctor, a Lawyer, or any other kind of advanced professional.
From the time one starts getting serious about learning music, expect it to take somewhere between 10-12 years to master all aspects of musicianship. Some people will do it more quickly, but this is a very realistic estimate for most aspiring professionals.