On most quilts, especially busy ones, I like to use 2 borders. It helps to stop the eye from wandering and frames it up nicely. A narrow inner border and wider outer border. I often do the inner borders in marbles or other tonal fabrics. The outer border I pick one of the fabrics in the center or something that blends with it well. I always audition them before I cut anything. Many times, I don't select a border fabric until the center is done.