The answer to your question depends on how you, as a grown-up, learn best. Some people can swallow great chunks effectively while others need to work on bite sized ideas, some people get stuff quickly while others have to really work to get it into their bones.i wouldnt say im organized but if i really want to do something i can just obsessively do it nonstop until it has been achieved
You need to work out a program based on how you learn best.
Either way, I'd suggest one of many online or book based theory courses. Within the western/jazz tradition - the core content doesn't vary that much. With YouTube you can find someone with an online courses based on whether you like the sound / style / attitude. Again, one size doesn't fit all. But you can also ask for suggestions here.
I'd suggest methodically working through the course till each chapter because obvious to you. Take your time. Keep going till you've done a chunk, till you decide if you're on the right track.
