The gun and the mask are the main part that is hand made, though I did have to do some sewing cause I couldn't find a jumpsuit that was my size.
Also I used duck tape to make the shoes.
The gun is made out of:
Foam rubber stuff that came as packing material, that I got at work, spray painted white or black
poster board spray painted black
a clear plastic handle sanded down to scatter light
a flash light to light up the plastic
some old wires I cut off broken headphones
and a lot of hot glue
I found a video online as a guide but I had to improvise a lot of the material.
The Wheatley mask is made of mostly the foam rubber painted and glued onto a face shield
and I made cup cakes to go along with the costume (it's probably a lie though)