What you need...
About 3m of fabric, sewing machine, elastic (possibly a needle and thread and a hook)
What you must do...
Cut two of the first (front), one of the second (back). The orange dotted line is where you might use a princess seam (refer to my 'wrap bodice' tutorial) but I don't think it's a big deal. Up to you. I've just done one because I have limited fabric and it's a way to... make the bigger piece without it looking odd haha. I've also done the same on the back but... JUST IGNORE IT. The length of both should be from your shoulders to the waistline, plus an inch or so seam allowance. Keep in mind that for the first piece, you will cross these over so make sure you make it a few wider. You can use an existing shirt for reference if you are unsure. I have not made this to be fitted - you should be able to pull this over your head so do make it wide enough!
With the right sides inward, sew the pieces together at the shoulders and sides, along the dotted lines. Set it aside for the moment.
For your skirt, either get one long piece of fabric or lots of panels that together make up one long piece of fabric, whatever you can do. I've heard some say the skirt should be 3x you waist measurement for adequate poof, but obviously that depends on the weight and type of your fabric / your own personal taste. Sew them together so you end up with a big loop / circle, and hem.
Either pleat or gather your skirt so the skirt opening and the bottom of the bodice are the same size. This should still be quite a bit wider than your waist.
Unfortunately I didn't photograph this part very well but it's easy to understand. Get your elastic and cut a length that is snug around your waist but not so tight you can't fit it over your hips. Sew the ends of the elastic together. Match the sewn part of the elastic to a seam on the skirt and sew it in place. When you pull the elastic taut, take hold of the loop on the opposite side to that you've just sewn down, and sew that side to the other side of the skirt (as in the diagram). Now, from one of the sewn points, sew over the elastic on to the already gathered edge of the skirt, pulling the elastic taut. As you sew, pull the elastic so it is the same length as the skirt. If you pull it too much or not enough, it will end up looking uneven. Keep doing this until the whole skirt is attached to the elastic and it fits you around the waist.
WHY are my diagrams always weird? Cut two of both shapes. This left shape is the collar, so it must match up with the neckline of the bodice as above. Wrong sides together, sew the sides of each piece together so it forms a big tubey thing, turn inside out and iron! Take the wrong side of the collar (the side which will face inward) and sew the edge to the edge of the neckline (wrong side against wrong side - any raw edges should be zig-zagged first!). Open the collar out the right way round and iron.
For the second shape, make sure the length matches up with the armholes. Sew the ends of each piece together so you end up with two circles. Hem one side, sew the other side to the armhole, matching up the seams.
This step is optional. If you have some hooks and eyes on hand (or just hooks, really), use a needle and thread to sew a little loop on one side of the collar, and a hook on the other side (you will have to do this from underneath the collar so it is hidden). This way you can make your dress a little less revealing quickly and easily if you so choose.
Anyway, sew the bodice of the dress to the skirt (right sides together) on the elastic in the same way as before i.e. pulling the elastic taut as you sew. You should now be finished.