*Edit: My lovely friend, who is much better at making patterns and sewing, helped me make a quick prototype dress. I included it in the main picture!
Thank you for voting these into the Dream It, Draw It, Wear It Contest Finals!
My first sketch started a little rough. I used the Pencil and Symmetry Y (Y key) to make each side even, but the lines were a little shaky, even using my old drawing tablet. I was drawing in Free mode, so I decided to turn on Steady Stroke mode instead.
I erased my first attempt with the Eraser tool. You can resize the brush size with the [ ] bracket keys.
With Steady Stroke on, my second drawing turned out a lot smoother, but it still needed a little refining.
By holding down the Shift key as I am drawing, I am able to make some of the necessary lines straight. Now that I am happy with the shape, I can start on the fabric design.
With Symmetry Y still turned on, I am able to get even lines of both sides and do half the work! Once I got all the stripes on, I was pretty satisfied with the design, but I wanted to add a little detail on the bottom of the arm straps. Blue and white stripe feels very nautical to me, so I decided to add an anchor detail. I made a quick vector of an anchor and added that image to the drawing (File>Add Image). I resized them to fit on the sleeves and added a larger anchor to show the detail.
I added in a note about the dress length using the type tool. Pretty easy stuff!