I'm a beginner guitarist (started five months ago), my goal is to be a fingerstyle player. On the horizon of two years, I want to be able to arrange songs. So what's are the essential scales and theory that I should learn and practice.
Well if you're only setting yourself 2 years to learn then I wouldn't bother mastering any exotic scales so I'd just stick with the following scales:
- natural minor
- minor pentatonic
- major pentatonic
- learn about chord building
- learn about chord progressions (including cadences) and what notes sound good over a particular chord in a progression (or more simply, over the whole progression)
- rhythmic techniques (such as note values, rests, time signatures, tempo/speed, rhythmic patterns, stressed notes/syncopation, types of rhythm [i.e. swing/shuffle], rhythmic cadences, etc...)
- learn about song form, in particular 32 bar blues and verse-chorus form
- learn about melodic techniques such as phrasing techniques, riffs, licks, runs, contour patterns, etc... there'd be different phrasing standards in different styles
The aforementioned points will teach you musicality but you also need to teach yourself instrumental technique which include dynamics and articulation, i.e. producing particular tones (vowel sounds) by picking the string in a particular way and/or at a particular part of the string (i.e. close to the bridge or neck), picking soft or hard, harmonics, percussive effects, hammer-ons/pull-offs, sliding, etc...
All of the above can be learned quite effectively by learning how they're applied in songs and playing those songs.
There's not much point in looking into anything too advanced in the first two years; it's one thing knowing a scale, or composition technique but then mastering them takes years of effort.
Cheers, Lost C.