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.
Upcoming Cons: Dragon*con 2013
Completed Cosplays: Naruto Uzumaki, Kiba Inuzuka, BB, Casual Prussia, Pajama Prussia, Daenerys Targaryen, Cowboy America, Mad Hatter (Original)
Working On: Denmark (85%), Asami Sato(0%)