i have to say i totally agree with bagginsbill, and he put it much more cogently than i had tried to.  i think the thing to keep in mind as you learn stuff and explore it on your own, that when you're testing specifics you think about generalities. 

the subtract node's properties are in the manual.  what you want is to have a feel for how to use it, and as bagginsbill has said, that isn't something any one can just tell you.  you have to learn it. what helps is coming up with problems, and then finding solutions.  you can have totally different solutions, and come up with similar answers.  even if they're not the most efficient or even most general, they can help lots of people.

just speaking as someone who has followed bagginsbill's works for a few years now, i think you should be proud of your explorations.  even when you're wrong, you learn a lot.  i'm too embarassed to share my own efforts, but i know i should be more open.  and from watching what you've posted, i don't think you should find your path easier or quicker.  as they say in one of my favorite toons, "there's no shortcut, no trickity trick, you just have to meet it head on." 

and the big thing you can keep in mind to sort of give you some boundaries is a focus on what you want to do.  one reason i end up exploring a lot on my own is that i like two extremes of lighting, and to do lighting very specific to my scenes.  i've started making my own props, finding my own references, so i have more and more specific interests.  i've got a small library of materials that combine parts of what i've learned from bagginsbill, my own experiments and other random stuff people have talked about.  you don't have to be bagginsbill; your experiments don't have to be general.  they can be for a specific image.  but i guess you know that since you've already started a learning community.