Re: using scales
Unfortunately, if you dive into a theory book all on your own, you risk just being overwhelmed. I remember buying that dreadnought "Guitar Grimoire" and just being confused. The rules in their basic form are really quite simple. However, it's not simple until you know how.. sort of like a bicycle.
IMO, the most important thing you need to do right this minute is to learn the names of the notes in all positions on the fretboard and learn the C major scale at all locations on the fretboard. I think you should proceed in this order.
1. Learn the 5 major scale patterns in the Key of C. (Some will say 7, my teacher taught me 5, so that's how I learned.) You can find these virtually anywhere either on the internet or in most books. These patterns will come up time and again when you decide to venture into other keys, modes, etc. They are absolute building blocks.
2. Next you need to learn the notes, and where they're located. This is going to sound ridiculous, but believe me it works. As you're playing through your scale patterns, you must say the names of the notes OUT LOUD. Saying it just reinforces so much more than silence. You will be surprised how difficult it can be to say the alphabet backwards G to A - and I still have to think about that one.
3. Get a beginning Mel Bay book. Go through it piece by piece until you can play everything. Repeat the names of the notes as you play. The first time through, you will learn all the notes at 1st position. If you're really serious, you'll go through the book again and again in all 5 positions (okay, 7) until you know your Cmajor dead on. (Hint hint - C major = A minor. Probably THE most popular rock guitar key)
Do not proceed any further until you've got that down. Don't overwhelm yourself with all the other stuff until you've got that stuff down cold. How often does anyone play the inverted Hungarian minor, double-dog whammy dare sooper dooper double pentatonic scale? You will get tons of mileage out of Cmaj (Amin) and Gmaj (Emin). Dozens of AC/DC songs cannot be wrong.