I'm working on two cosplays along the same line as you, all I can say is tier 3.
To make the shoulders I would suggest make a wire mesh, cover it, and paint. For the covering part, you could use foam, paper mache, fiberglass, wonderflex, or vinyl. Choose which method you would like to use then look around for tutorials on howto do each method.
~Yuni's the name, Prop's & Armor are my game.~