I would suggest going as any outfit you want to go in. Which ever you think he would look better in. I personally like the blue or green one, but that's just me.
About the hair, dye it and go natural if you want. I personally haven't seen very many good Germany wigs unless they were commissioned. I know many guys wouldn't dye their hair, but once again, with whatever you feel comfortable with.
About the friends, if you want to cosplay than cosplay. They don't have to if they don't want to. It's 100% your choice.