The fun part about modes is that they really open up, not restrict, the type of chords you can play. To keep things sounding dorian, emphasize the characteristic notes, the major sixth, the minor third, the flat seventh, and especially the root. If a chord based on one of these notes sounds better as major or minor, don't worry so much about keeping everything diatonic, just play what sounds right. To make progressions, you can experiment with stacked fourths ala Miles Davis. You may notice that these stacked fourths form the cores of other chords. You can play with this idea a bit, and modulate to new keys based on these chords. In short, don't let strictly adhering to the diatonic dorian mode restrict what you play.
