try putting your question on a more active forum like landscape design.

Carex pensylvanica, partridge berry, and wintergreen are the three plants that grow naturally in semi to full shade here. Nothing will keep buckthorn at bay - you'll need to go out a couple of times a year with pliers and pull all the sprouts. Using mulch while you wait for ground covers to grow will help. You may be able to get for free chopped tree trimmings from the folks who cut back around the power lines. I just stop and ask when they are in my area, and give them my address, and they drop them off since I'm closer than the dump.