For mostly panfish flies I would get several colors of marabou. especially black, olive, red or orange and yellow. You can use it for tails on woolly buggers or to make leaches. Shredded a bit and put in a dubbing loop it makes a very buggy nymph dubbing. Hen necks make inexpensive soft hackles and can be used for collars or beards. You will want some chenille for woolly buggers and to make some nymph bodies also. Get some peacock herl and a hares mask because they just plain catch fish. Add a couple of cheap saddles some floss and an assortment of hooks. Then go to the craft store and get some ribbing wire in the beading section and some craft foam sheets in assorted colors for gurgle pops (see fly of the week archives). You could get a lot more and some folks will suggest other things but that will get you a lot of panfish flies for not a lot of money