not that I am an expert at doing feathers (i too am learning) but I am expert at reading about it!
What I have read so far is to use a thinner 60 weight thread (say bottomline, there are others) and use a thread that blends in more with your fabric and your mistakes errr design decisions wont be so visible..see... problem solvered.. at least until you practice more...lol..and anyway I think you first practice piece is pretty good so just keep practicing!