Once you have the fabric and all your measurements, fold the fabric in half length wise.  Lay the fabric out of a flat surface and make the following lines using your measurements (see graphic).

 

 

It may be a little easier to mark and cut the body before making the measurements for the rest of the dress.  Now is also a good time to work on the neck hole since you don’t have as much fabric to deal with.

 

Once you have all of the lines marked, cut out each piece of the dress along those lines. 

 

I would recommend starting the sides by sewing the long gores to the arm pieces along the number 4 measurement.  Next sew the two arm pieces together along measurement 6.  After that sew the two arm/gusset pieces to the body.  Finish the dress by sewing the two sides together.

 

The only thing left to do is hem the bottom and the sleeves.