For this floor length caftan, you need approximately 4 yards of 45” wide fabric. I have not directly experimented with stripes or one way designs, so I don’t quite know what extra yardage would be required to that. But generally, 4 yards is all you need. That’s it! First, fold the fabric not on the grain, but on the cross grain. This will leave you with a double thickness of fabric that is 2 yards long.
For this I use pattern weights, but if you prefer use pins. I use a crayola, washable pen to mark the outline of each piece as I go; however, if you are not comfortable marking directly on the fabric, you can cut each piece as you go. For demonstration purposes, I am cutting the piece in two stages. However, I recommend that all pieces fit on the fabric before cutting anything out, as sometimes a simple rearrangement will result in everything being cut out just fine.
Both the gusset and the gore require 4 pieces be cut, so I trace one set, flip the pattern pieces so the diagonal matches, and trace it again, before cutting it out.
So there it is. Four pattern pieces, 11 total cut pieces. For the TL; DR, here is the video of the process, from layout, to tracing, to cutting out.