I'm a pretty big fan of tent dresses (or trapeze dresses - call it what you want). They're simple, easy-to-make and you can have many variations of them. These are a fun style to wear for spring and summer!
See this DIY from a Good Housekeeping Crafts book from 1971 - photos at the end of my own trapeze top from a while ago! (Bear with me on the photos here - this book is quite cumbersome and hard to scan.)
Applique patterns, in case you wanted the dress to look EXACTLY like the photo. (But why?)
How to cut the fabric efficiently. (This is actually pretty important cost-wise for you - especially with something this big.)
Using pattern instructions from my patternmaking book from college, I created this swingy trapeze top a bit ago. I used sweater fabric from a thrift store find for the collar of this top.
I also opened up the back on the pattern to have a diamond shape.
It can easily be belted like in this photo for a blouse-y look. (Photo by Jane Chu.)
Have fun, kids!