I’m a self-learner too, and in the same boat you are: I don’t have time or money for a teacher. But I’ve found a process that’s worked extremely well for me. It has as much to do with approach and perspective as anything else, and maybe there’s something in it for you, too.
Here’s the thing: I don’t believe your focus should be one field or another, either technique or theory, learning new pieces or composing, exclusive of all the others. I’ve found the most productivity from taking them all together. When I get time for a good, focused practice session (a free hour or two), I’ll warm up with scales and arpeggios, either running through the Circle of Fifths or what I call “scale exploration”—taking a single key and running through all its different aspects (pentascales, pentatonic, blues, whole tone, etc.) and its major chords (including the extended jazz chords). I’ve written up sheets laying out these elements in each key . . . which, when I did it, was another way to work on theory. Through all of this I’m sharpening my technique, which is my rustiest area. If I can’t play the pieces I’m studying, how’s my ear going to improve?
Then I’ll work on playing. I’ll usually start with a piece or two that have grown comfortable to me, as a way of encourage myself that I’ll be able to reach this point with the next piece I’m working with. Then I pull out that next piece and start sweating through it. I hit the difficult passages, smooth out the ones I’m getting better at, play it start to end at least a couple of times. I don’t expect to finish at the point of perfection. I do expect to see visible improvement in at least some areas, and I don’t let it go until I’m satisfied that’s happened. After this, I’ll toy a little with a piece I’ll be tackling after this one, just a quick glance at the road ahead (and prep for the next step in my practice). I’ll end this part of the session playing one of the comfortable pieces again—once more to remind myself that I can eventually reach this point with any piece I put my mind to.
Then it’s time for theory. I’ll usually turn to that “road ahead” piece and start to break it down. I spot the key, look for modal possibilities, identify the chords (by their number within the key), analyze the progressions, watch for modulation, look at how the melody plays against the harmony. This serves two purposes: first, it increases my theory fluency. I’m learning not just how to play music, but how to meaningfully read it. Second, I’ve found that taking this extra step makes it immeasurably easier to learn to play the piece when I start wrestling with it at the keys.
[Side note: My first productive experience with this was when I deconstructed Rohan (just like the orcs tried to do at Helm’s Deep, I guess). I took the theme Howard Shore composed for Rohan in The Lord of the Rings (“King of the Golden Hall”) and broke it down. It was a toughie; there were no accidentals in the signature, so it looked to be in the key of C. But it followed a weird progression that included the D major chord—changing what would’ve been the ii chord into a major one (a “II” chord), which shouldn’t be the case in C. Then I noticed that every F along the way was sharpened, so I thought it might be G. But that D major chord should still be a minor (the vi chord). Since the fourth note’s raised half a step through the whole piece . . . Waitaminute! It’s the Lydian mode, fercryinoutloud! That was a breakthrough moment for me. Up to that point I’d struggled a bit when attempting to play it. After that, I literally had no problems performing the piece, because I fundamentally understood how and why every part fit into the whole.]
After this, I may also do a little composing if time allows. Nothing big; usually just putting a melody over a few bars of harmony. I’m not trying to create a masterpiece. It’s all about application—putting what I’ve learned into action. That’s a key element in the learning process.
I try to allow for all of these steps in a practice session. When I’m crunched for time, I may only get to a step or two in, maybe a quick warm up and some playing, or working a piece on paper (theory) and on the keys at the same time. The point of all this is that you shouldn’t necessarily limit your focus to just one thing. You’ll learn faster and with better results if you approach music as a whole instead of piece by piece.