The Weeping Angels' dresses were the easiest for me to think on how to construct it, and actually create. Ktar and I made each of our dresses a bit differently... (I made mine a tad "off" but it doesn't actually bother me, I'd rather be a tiny bit different, haha)
First, I figured we needed to figure out how much fabric we needed on each dress. I had a bolt of heavy weight muslin which I dyed grey using RIT dye (since I was feeling lazy, and didn't feel like using MX dye and stirring it for an hour >>;; )
Each dress used about 3 yards or so of fabric. Mine used a bit more because 1) I'm a bit bigger than Ktar, and 2) I made mine much more full around the skirt.
To hold out the bottom of the skirt, and to make it look more "statue-like" I nabbed the idea from Penwiper to use a hula hoop in the hem of the skirt. I cut about a 8 inches out of the hoop to make it a bit smaller and more manageable. I then used contact cement to reattach the hoop ends, and taped it for good measure. The cement made is sticky without being permanent, and the tape was removable, so that I could remove it from the hem if I needed to.
First, we made the lining layer, to which all of the gathered parts would be attached. To make this, we needed to figure out how much fabric we needed to use for the skirt. We figured out the circumference of the hula hoop we were using for the bottom, and the circumference of where we were going to have the skirt attach at the waist. Cutting out the fabric, we were a bit close on getting both of our dresses out of what we had, so we had to do some creative cutting. For mine, I had to have a seperate bodice and skirt, instead of making a kind of tube dress like I had originally planned.
To cut the skirt pieces, we divided the amount we needed for our waists divided by 4 and added an inch to it or so, and measured from one edge that number, and also from the opposite edge, cutting between them. Like this:
For the outer skirt, I multiplied my waist measurement by 2 to get the amount of fullness that I wanted, which gave me enough fullness to also go over the hula hoop and still have some gathering at the bottom.
I just kind of made up the dress as I went, cutting and fitting it until it looked the way I wanted it to.
(If anyone wants more detailed instruction on "my way" of making things, I'll write something up.... it's kind of funny/embarrassing actually. >_>;;)