Guitar players usually use a capo in DADGAD. If you know D major and D minor scales/chords, you can play in any key (see table above, PDF download).
Knowing the fingerings of the other modes will allow you to be more versatile, to be able to choose if you want to play with or without a capo, to build a better chord repertoire and also to learn other combinations.
Which capo to use? Quickdraw (photo 1) or Jim Dunlop (photo 2) are very useful, because they slide easily up and down the fretboard. Otherwise Kyser capos (photo 3) are very good too.