Learning vamps is a great way to get to know a new tuning and find ways to move between the I and V chords (D and A7 in the key of D). Memorize as many of these as you can and add your own ideas.
Tuning: DADF#AD
If your are interested in more lessons like this and further development, you can become a member of the Slack Key Guitar Workshop and get access to all the materials including sheet music and tablature for each lesson.