I have been playing the guitar for many years yet I find music theory elusive. Consequently, my musical vocabulary is limited. But I still love to improvise and, through trial-and-error, compose music that I think sounds good. Sometimes I get lucky.
I'm wondering if there is an approach to learning music theory by applying it to my haphazard composition "technique." For example, I would love to be able to collect an assortment of chords and scales that are theoretically compatible, and then experiment within those constraints to build a composition. I have the Guitar Grimoire and some other resources, but I find their scope too broad and intimidating. I would prefer to "dial up" a set of tinker toys in a particular key to play with, for lack of a better analogy. Where would I start?