Ooh I love doing this.
I think the latest thing was a costume for sozlet for her school play. Not that interesting but it was fun. She had to be a rather snooty rich lady from the 1850's (the play was about the underground railroad, she was the villain). We researched costumes online, and the main thing I made was her big skirt. She already had a hoop skirt, I used some curtain material I'd bought at Ikea for $7 (yards and yards of it) that looked like a silk (but really was nylon or something). I measured her waist, and then used blanket edging (you know, satin that is folded over) as the waistband.
I just freehanded the pleats -- pinned the edges to the waistband first, then found the middle of the skirt fabric and pinned it to the middle of the waistband, then the next section halfway between the middle and the edge, etc. (Hard to describe, might not be clear.) Ended up with pleats about every two inches, evenly spaced.
Pinned it to the blanket edging with the edging open, then closed it and re-pinned so all the pins were on the outside. That was a little tricky.
Sewed the skirt to the waistband, then velcro on to the edges (lots of measuring and re-measuring here).
The bottom edge was already finished (since they were meant to be curtains) and one side was already finished, since it wrapped in the back and was just a costume I didn't finish the other side (it was under the finished side when fastened). So the whole thing was very quick and easy, under an hour start to finish.
Rounded it out with a high-collared shirt from Old Navy and a pearl brooch. And Charlotte Bronte hair (swoopy on the sides, bun in back).
The shirt ($12) was the only new purchase.