Basslines usually focus on the "root" tone of the chord that is being played. AutoTheory's Smart Scale shifts the "root" to the first white key in the "Chord Tones" and "Dynamic Scale" mappings.
While using a simple "root" oriented bassline works well alongside a more complex melody, sometimes you want your bassline to have more movement. When doing this you still want to emphasize the "root", while implementing the same melody techniques mentioned above regarding chord tones and non chord tones.
When using a bassline that has a lot of movement, it is probably a good idea to limit the movement of your melody. A simple melody with less tones that sustain longer will complement an active bassline well. When your melody and bassline are both moving around a lot, it often leads to conflict. A good technique to use is going back and forth between an active melody, and an active bassline.