Learn to read music.
Even if you’ve got a beautiful voice, if you can’t read music, then you’re illiterate for the purposes of your dream career in music. Knowing how to read music helps you communicate with other performers, write your own songs, and deepen your knowledge of the art. If you don’t get a formal background in music, then do some independent study to learn how to read music and understand the basics of music theory (rhythm, harmony, etc.).
Note that many gigs will require you to be able to read music, so this is an essential skill.