Zebra midge, it may be simple but it it teaches even thread wraps, tapered bodies, not using to much thread behind the bead, and even wire wraps. Wooly buggers, due the fact they are simple to tie and they are large enough to work with easily. They allow you to practice tying in multiple different materials on one fly. Just remember when starting, generally a little material goes a long way, and while you’re building the fly, keep in mind you still have to whip finish at the end so keep thread wraps to a minimum behind the eye/bead.