this may just be the cutest dress in existence. and you should make a tutorial for it
Well, I can't really do a full tutorial since I didn't take progress pics, but let's see what I can do shall we? This isn't super detailed since there's no pictures, but it should give you an idea on how this goes together.
Okay, so you'll need a pattern that you can use for a bodice - basically any fitted bodice will do, cut this pattern off at the waistline if it isn't already (with seam allowance of course). Cut all the pieces normally, except the back piece. You want to measure the narrowest part of the back pattern piece, double that number, then measure that amount away from a fold on your fabric. Lay the back pattern piece like you're going to cut it on the fold, but place it the amount you measured away from the fold. Pretty much you want the back to end up being extra wide so that you can add the shirring in the back later.
Sew the bodice up like normal, and do the same for lining (not optional if you want to do back shirring with this method), but don't attach the two yet. For the top ruffle, cut and sew together into a loop some strips that are double the height you want the ruffle to end up plus seam allowance (you want to fold the strips in half so the ruffle has no raw edge on top) and twice as long as it is around your bodice. Fold in half and gather/ruffle that.The tricky part: Before you gather it, measure how wide your new/expanded back section is, without seam allowance, and mark that distance on your strip. You don't want to gather this portion since it will gather when you add the elastic in the back later. Sandwich the ruffle between the lining and outside bodice, lining up the un-gathered portion with the back panel. It should stick up when you flip it right side out. You also want to sandwich the straps (cut according to your bodice pattern) in this same seam but only in the front. If you want the straps to cross like mine though, you'll have to add some extra length to them while cutting out.
The skirt is a basic gathered rectangle. Mine was two rectangles the width of the fabric (42") by 15" or so. The pockets in the seams are pretty much rectangles sewn in like normal in-seam pockets (there's tutorials for this floating around). I added button holes to one side of each pocket, about and inch and a half away from the edge before I sewed the pockets in to the skirt. So, sew in your pockets and sew the front and back of the skirt together.
Cut some more strips for the bottom ruffle, this time about 5" or 6" high and double the distance around the bottom of your skirt. Sew these into a loop, hem one edge, and gather the other one. This gets gathered evenly all the way around and sewn to the bottom of the skirt.
Then gather the top of the skirt so that it fits the bottom of your bodice. Like you did with the top ruffle, you want to measure a section in the center back of your skirt that is the same size as the back panel of the bodice so that this section is not gathered when you sew the skirt onto the bodice.
If you want to line the skirt too not just the bodice, cut two rectangles for that too and gather and sew on the same way, the only difference is you don't need to do a bottom ruffle on the lining. Sew the lining to the bodice lining and the outside skirt to the outside bodice.
Now it should pretty much look like a dress, except be way too big in the back. This part, the shirring, is kind of tricky: measure the height of the back panel, divide it evenly into however many lines of elastic you want to have, and sew lines across only the back panel through the outside and lining fabric. The first line you sew will be 3/8" away from the top of the bodice (not counting the ruffle) then one however far down you measure will get you even divisions, then 3/8" down from that one, and so on, so that you end up with a number of evenly spaced channels that will fit 1/4" elastic. The last line of stitching should be right where the bodice and skirt join.
Next, thread some elastic through each of the channels and sew it down on one side. This line of stitching is perpendicular to the channels, right on top of where the back panel joins the side back panel. Make sure it goes over all the elastic ends so they can't slide out. Safety pin the elastics in place on the other side of the back panel so you can try it on. A good starting point for how long each piece of elastic should be is 1/2 of what each channel measures since elastic usually stretches to double it's length. Try on, adjust the elastics in the shirring, and once it fits perfect, sew the other side of the elastics down, right over the other back panel to side back joint.
Try on your dress, and see where the straps reach in the back and where you want them. It's nice to have someone help you with this so they can mark where the straps will button on while you're wearing the dress. Make some button holes in the ends of the straps, and put buttons where the straps meet the bodice on the inside, and there you go!
Hope that's at least a little helpful to someone