I play in both 'E' and 'G' tunings with a couple of extra ones thrown in as well, when I need certain riffs to play a melody. Here's a couple of things That might help you in your quest: Learn good slide technique. Learn how to damp the strings that you don't want to sound with either the side of your right hand, or the free fingers on your left. I know it sounds complicated, but it's essential to getting a good tone. You'll get it eventually if you really try. Learn a few chords in open tunings. Grab your guitar in open 'E' or 'D' and try this: I chord: open. IV chord: 1st finger 3rd string 1st fret; 2nd finger 5th string 2nd fret; V chord: 1st finger 4th string 2nd fret, 2nd finger 1st string 2nd fret, 3rd finger, 1st srting, 2nd fret. Relative minor: 2nd finger 5th string second fret, 3rd finger 2nd string 2nd fret.
Happy fretting!