Well.. My friend had cosplayed as Temari, and usually when people do her hair they don't make the little ponytails actually stand up. If you want it to be really accurate and don't mind a little bit of discomfort. You can break little wooden sticks.. I think, you should use something like a toothpick, and stick it stick it into the ponytail in the middle of where the hairband is, and use a little bit of hairspary on the ponytail..to make it look spiky as Temari-San has it. (the toothpick thing, is there to make sure it stands up straight out, and the hairspray helps keeping it together) And pretty much do that for all four of her small ponytails. As for buying the actual wig, ebay has some pretty nice wigs. They are pretty cheap, yet made out of really good materials. The material i would suggest, is Kanekalon synthetic fiber, thats what all my wigs are made out of and they are easy to style and some people have thought it was my actual hair.
Gomen for my lack of better wording, i've never been really good at explaining anything.. x_x