Those are both nice areas. The Necklace Valley is a much longer walk and gets more traffic, though both are popular areas. The Necklace Valley area is a bit more scenic. Both areas offer lots of lakes to fish and you really won’t go wrong with either area.
Elk hair caddis is my favorite dry fly. It never hurts to have some of the other basics like Adams, Coachman, etc. Bring along some Carey Specials, Wolly Worms, or Buggers, and some nymphs if you need to go sub-surface.