Let me see, I have studied electric guitar for more than a year and played wood for more than a year. Now the piano on the market is in a mess, and I don't know how to start ~!
Music theory is very important! Especially the ear. Otherwise, you will never understand those endless scales. Be sure to take time to practice solfeggio and hearing. If someone plays a random note on the guitar, you will know what it is. Actually, it's not hard to say it. I am ashamed that my son began to learn piano at the age of six. If I play a note on the guitar casually, he will know what the name is, and he can tell me which string I'm not sure about. I don't feel as good as him, just because I don't practice my ear sounds systematically.