Re: Whats next???
I think flies should be chosen so they are skill based. The next skill you should learn is dubbing.
You could try a brassie next. Then a serendipity. Both are simple flies that will catch fish.
Then could try a simple fur nymph to learn to dub a body. Nymphs can have rougher and imperfect bodies and still catch fish. From a simple fur nymph go to a GRHE. Then a pheasant tail.
A pheasant tail IMHO is much too difficult a next step right now. A PT means you need to learn to select the right number fibers for the hook size, tie a tie of the right length, wind the body to the proper point and to tie a wing case and legs. Way too many things to go wrong.
Then try a fur ant to teach you to form a dubbed dry fly body and wind hackle; or an EHC dry fly to teach to tie a tapered dubbed body and the elk hair wing.
"Discovery consists of seeing what everybody has seen and thinking what nobody has thought"..........Szent-Gyorgy