I think you should first learn to make barre chords (cause then you can make ANY chord by moving you hand up or down the neck or by liftin or adding a finger), learn a few movable scales (your hands are already in position when you make your barre chord) and learn your open chords which sound soooooo sweet on a 12 string.
That sounds like a lot but heres a good method:
1)Start with power chords useing the E, A and D strings. If it feels like a strain or an awkward stretch thats because it is. Don't worry, it will be second nature fairly soon.
2)While you are mastering that, start working on the minor scale it is easy and very versitile
3)As you are learning those 2 things, pick an open chord to learn. Practice making it until you can play it clear and clean with no buzz or muffled sounds (assuming the condition of you guitar doesn't cause those sounds.) Practice going from power chords to your open chord quickly and smoothly. As you learn each chord add another and another.
4)Once you have mastered step 1, make the same power chords on the A, D and G strings.
5)By now you should have your minor scale down pretty good. If not, it's ok keep working at it. Now you can add the major scale, also very simple and very versitile.
6)By this time you probably have some hand streangth, mobility, dexterity. You will need all theese thing because now we move to barre chords. Remember your power chords? geuss what? thats half of a barre chord. Just barre that finger accross all the strings (if you aren't allready) and add or lift your middle finger or pinky. Take your time and do it clean and smooth.
7)get in a band and show off your mad guitar skills! Don't forget to pick up little things from others on the way.
"Nobody paints by ear so why would I play guitar by sight?"