#1
I have learned E A D power chords, E A D G C major chords, E A D minor chords, E A D G C dominant chords, and learned how to move most of them up the neck using barre chords. I'm still fairly slow at finding them, and I occasionally miss a note if I try to move between them. Should I keep practicing them and not learn anything else until I have mastered them? Should I try to learn a simple song using these chords? I don't really know where to go from here. Thanks.
#2
try to learn a simple song using those chords, so that you have something fun to do besides just boring drills, but at the same time, it's all part of practice, practice, practice.
When life gives you lemons, squirt juice in your enemies' eyes.
#3
I would start finding some songs to play. It sounds like you have learnt more than enough to play a few songs. You will find by playing more songs you will improve quickly and learn new chords and techniques. I couldn't even play the songs I now use to warm up with when I first started playing.