Do I put a liner before I use waterproof drywall when I prepare for a custom shower

So are you tiling this shower, no drywall or greenboard goes into this wet area. You can use cement board, Hardiebacker or the schluter system Tile Shower - Schluter-Systems (http://www.schluter.com/4625.aspx) If you go with cement board or Hardieboard you do install a water barrier first on the studs, I use 10 mil visqueen