Some simple flies to tie off the bat are San Juan Worms, Griffith's Gnats, Wolly Buggers, Wolly Worms, Sawyer Nymphs and CDC and Elk flies. All of these flies are pretty simple and are quite fishable even if they don't turn out perfect. My first fly caught trout was on a little size 14 griffith's Gnat I tied the first week I started tying.
Good luck.