It depends on your existing skill set. If you are a complete noobie, you will benifit from any beginners lessons from yamaha or CC or any private music school.
Theory is quite important as it's the foundation on which you built your skill.
It helps you 'grow'.
If you already got those, I'm afraid it's quite difficult to find a suitable teacher to progress your skill. Maybe easy to find teachers to teach you techniques you never tried before, but mostly can be found on books or video courses.
Of course, it's like bodybuilding, practise makes perfect, if you learn new stuff but only spend 10mins on it everyday, will take forever or loose patience. Most do as they just fall back to what they are comfortable with. You must commit 1-2hrs per day maybe take 1 day off per week.
I heard that the pros spend 8/10/12/14 hrs a day on the git. So depends to the individual.
Good luck on your endeavors.
NB. Don't mind me, my skills are not in music, more to the craft instead.
Regards,
Mike
Mikemann Music Studio