I know that there's probably a million tutorials for tutu skirts already on the internet, but this one contains a few shortcuts so hopefully I'm not just repeating what everybody else has said.
I made this skirt last week:
It's a pretty crazy skirt but it would be easy to tweak it or tone it down. If it was made longer, or with fabric that wasn't so stiff, it might pass off as a somewhat normal goth/alternative style skirt.
I started out with the petticoat portion of an old wedding dress:
This was the main shortcut. I cut the bottom layer of ruffles off the petticoat to use for the tutu. Thrift stores usually have a lot of different pleated or ruffled dresses and skirts. If you like the fabric of a thrift store skirt but not the general fit or style, it is super easy to just cut off the ruffled part and add a waistband of your own.
I didn't want the white tulle to have a raw edge, so I grabbed a big spool of ribbon and sewed the ribbon to the bottom edge of the fabric. I didn't use pins or even measure out the length of ribbon I needed. I just unrolled the ribbon spool as I was sewing. This is the same technique that I used to make bridal veils while I was working at a custom bridal gown shop last year. This works for any type of fabric that will not fray if left with a raw edge on one side. I also stretched the tulle slightly while I was sewing it to the ribbon so that there would be even more volume at the bottom of the skirt.
The gathered tulle from the wedding dress wasn't ruffled enough for me, so I decided to gather the fabric up even more. Instead of using the typical home-sewing gathering technique, I used another technique from the bridal gown shop. I folded small pleats into the fabric as I was sewing it. This is an easy and fun way to make fabric ruffles if you don't need the pleats to be perfectly even.
Here's the end result of all the pleating:
After sewing the tutu part of the skirt, I started laying out different fabrics that I could use for the waistband. I opted for some magenta plaid spandex plus some grommet tape trim. Since the spandex fabric was so stretchy, I made the waistband 4 inches smaller than I would have if it wasn't a stretch fabric. This way the fabric can stretch around the body and the skirt won't just slip off.
This skirt is a size small. The final waistband dimension was 28" around (to fit a low waist measurement of 32"). The tutu part of the skirt was about 37" around, so that it could stretch enough to fit over a 36" hip. I stretched the waistband fabric while sewing it on to the tutu fabric. I pinned it in even sections so that each part of the skirt has an even amount of gathers. After this, I added the trim and the lace-up part. The skirt doesn't need a closure because of the wide hip measurement and the stretch waistband.
You could use these same techniques for a much longer skirt. If you don't want such a poofy skirt style, you can use fabric that is not as stiff. A simple thin cotton fabric could take a large amount of gathering without creating too much bulk at the hips.