If you are good in drawing, you could start with a render of a human body from Poser or the free DAZ programs (both 3D). Export the drawing to Photoshop and then draw the dress over this image.

Wacom tablets are great to work with - it will feel more like pen or pencil - so much easier than using a mouse, which is so unnatural.
You do not need a large one to get started.

I am using a very old Wacom tablet, it is about 12 or 13 years old now and still working well.
The only drawback from being so old is that no new drivers are written for like Vista and no it does not support pressure sensitivity anymore.
Jacqueline