Hmmm good question....
What instrument(s) do you play?

Although I have self taught most of the instruments I play and have learned a ton on my own, I have also had weekly piano lessons for seven years. This has given me a solid foundation for how to practice and play, and especially how to sight read, so if you feel that you do not understand music or how to practice, a teacher might be a good idea.

You could try to record, and maybe arrange, a song with maybe two or three parts and see what you feel like you are lacking in skill. This is what I do to see where I need to work on next. Or you might find that you like what you hear and can start performing, you do not need to be perfect, just good enough to be somewhat confident in your skills.

I also highly encourage you to try to transcribe a few phrases of some simpler song, and than try something a bit harder, and then a bit harder...

Play music if you are a player (by yourself if need be, with other if you can, since that will put your listening skills more to the test), compose music if your are a composer. Ear-training by itself won't make you a better musician, but only as part of a full, ongoing musical practice. Interval recognition has definitely improved my accuracy in choir, for instance.

Advice above is great!! I would also add patience…!