I'm sort of on a Disney princess cosplay binge, so give me a break! (or, blame @Angelipon since her photos are so cute ><).
Anyways, I just came across this LOVELY cosplay of Jasmine from Aladdin, and I am so impressed by the wig--that poof! Those perfectly sectioned clumps of poof are amazing! So, I thought I'd look and see how people usually handle Jasmine's ridiculous hair :)
Since that didn't tell me at all how the hair was done, I thought I'd look for how cosplayers handle it. In this cosplayer's photo, you can see that you need a very thick wig, and have it rolled in the appropriate way so it really poofs around the face! If you use your own hair, I don't think you could get it as thick as needed, you know?
One solution might be to do what this cosplayer did, and go with the "Jafar version" of Jasmine! She just has a pony tail, though it is a REALLY thick ponytail. This would still be easier (in theory) to replicate when comparing to the poof sectioned version.
If you're going with the sectioned version, though, you have to make sure you have enough thick wig hair like this cosplayer does! The sections stand up to the poof, and they look like they're actually full enough!
You can still make it work with a slightly less thick wig, but I think you have to tone it all done like this cosplayer. She made it have less poofy sections (so they can still each decrease a little bit in size) and the poof around her hairline is smaller, too, but it all still looks proportionate!