Your armature for your FCG can be constructed of wooden dowels or everyday wire coat hangers.  You can measure yourself for the shoulder and arm section lengths or you can just go with the standard of 14 1/2" for the shoulder width, 11" for the upper arm, 18" for the lower arm and 10" for the neck to top of head length.

If you use dowels, you can install small eyebolts to the joint ends of the arms and shoulder.  The eyebolts can be joined by opening one eye and inserting the other bolt.  This will give you a swivel at the joint and keep the FCG from binding up.  If you use the wire coat hanger method, make sure you make an 'eye' at the ends to attach the piece together.

If you are using a styrofoam head, use a long piece of metal (big screwdriver or knitting hook will work) to poke a hole from the top to the bottom of the head.  The coat hanger will be bent in half and the bend will be extended to the top of the styrofoam head.
You can also get the sculpting wire mesh from a local craft store and form the mesh over a styrofoam head or your own face if you wish.  This can be installed in lieu of the styrofoam head and will give a see through look to the FCG.

Cheesecloth, scrim, gauze, etc can be used for the etheral effect of the ghost.  Many kinds of materials will 'blue' the fabric to make it glow in the dark such as RIT whitener, tonic water, etc.