Lots of good suggestions on flies so nothing significant to add on that topic.

However for flyline and leader setup I like a floating line and a 9ft leader and I attach a strike indicator (essentially a bobber) to the leader. The indicator has two functions. First it aids with strike detection; crappie can be notoriously light biters. Second, the indicator is used to suspend a weighted fly at a known depth. I prefer indicators that can be easily repositioned on the leader. If I need to use a leader longer than the length of the rod I use a slip indicator (slip bobber) that will break free and slide down the leader when a fish is hooked. Then I can fish longer leaders and reach a greater depth if needed. Slip indicators can be made but I have also acquired some from Cascade Crest Tools. There was quite a bit of discussion about slip indicators on this forum a year or two ago. I first learned about these techniques from an article in California Fly Fisher magazine many years ago and they greatly improved my success with crappie.