For the back straps, I'll suggest two options: use flesh colored elastic, which is what you see on dance costumes and so on. Or, get something pretty to connect them: a string of rhinestones or beads, ribbon, etc.
Your best bet might be to make a "skirt" that starts at the top, then just drape a rectangle (or two) of fabric over your chest until you get the look you want, then tack it down. You could attach the skirt to empire or bra-shaped top, then do the draping, which might give a more fitted look. Practice draping with a scrap, then if you need to trim a little to get it right, you're not using your good fabric.
It depends on whether you want to be able to see the zipper or not. If you're okay seeing the zipper, you can stay-stitch a half-inch wide U with square ends, and then slash it open with diagonal cuts to the corners, turn under and insert the zipper. This is a little tricky because you might have a loose thread in the corners.
Or, you can face the opening, which will make a nicer finish, but which will make the seam allowances thicker. You can do this with iron-on interfacing. Stitch, slash, turn, iron.
If you don't want to see the zipper, then you do the same thing, but you put a folded strip of fabric on top of the zipper, under the wrong side, and stitch it in at the top and along one side. You could get the fabric from an old pair of jeans or denim shirt, or use a contrasting fabric.
One final suggestion: if the zipper tends to scratch your legs or your boots, put a length of grosgrain ribbon on the inside to cover it.
As usual a picture is worth a thousand words, but I can't draw and there are copyright laws about anything else. A good sewing book in the library should show you what I'm talking about, if it isn't clear.
I think most of us get that way sometimes. Sometimes I'm in the mood to just look, and sometimes I'm in the mood to work. It takes a while for me to cut into expensive fabric. It's easier to use less expensive materials and say, "What the heck, I just want to see if this works." I've made some of my favorite things that way.
Some ways to help with a slump might be to go to the library and check out some books on crafts, or art, or design. Go to an art museum (or better yet, the gift shop, where there's always lots of inspiring things), or a craft fair.
AstroZombie138: you've probably heard this a dozen times, but if there's a class or workshop you could take, you might meet some folks with your interests and you'd be in an environment where the instructor isn't going to let you mess up. You might not make a lasting friend, but you'd definitely feel connected with the others in the class. It got me going after grad school. I didn't have time to do anything while I was in school, and needed a little jump start after I finished.
It almost looks like the ruffles are a really light-weight fabric that's been folded in half (but not pressed), which would cut down on finishing the edges, but might make gathering and stitching trickier. It would need to be very light-weight, or it would weigh-down the skirt, and you'd feel like you were wearing an old canvas tent.
Look in the costume sections of the pattern books.
Go to the library and get a book on making simple costumes. They'll have a diagram or instructions for a cave girl/Indian princess kind of thing that you can adapt.
For the fabric, use fleece or fake fur. They won't ravel. If you can't find what you want in a store, the auction sites will probably have something. Fake fur and fleece can be a little pricey. Any fabric that doesn't ravel or "fringe" badly could work.