Hmm... A wig under 30$ at that length/style? I doubt you'll find one that isn't a rats nest to be honest. ):
Might work, but I have a cosworx wig and to be honest... It's not that awesome. The fibres come out very easily when you brush, even if you're gentle.
So, if you have blonde hair or even light-ish hair, you could get temporary dye (like natural blonde spray or comb-in, since Agitha's hair is pretty slick) and style your hair into two buns with bangs. And then get loose hair and make falls to put over the buns. Does that make sense?
Like, I make dreadfalls, and they're attached to a hair elastic. Made to go over a small bun or ponytail as decoration. That might work well for her pigtails if you backcomb some of the hair in the middle and then style it over the voluminous inner parts.
Wow, I hope that made sense. :O