Breast Expanders, how much to fill first time?

This really depends on the mastectomy flaps.  Putting too much fluid in an expander can compromise the blood supply to the mastectomy flaps and cause necrosis of the flaps.  Most people generally start with 50-100 cc.  I believe it is wise to stay on the conservative side as flap necrosis can be  a terrible problem.  

There is no standard for the amount used.  I use anywhere from 50cc to 100cc per expansion. It all depends on the skin quality, size of expander, and goal volume.  Good luck on the rest of your expansion.