When DD was this age she loved to read, so Barnes and Noble or Books a million gift card. She still ask for this today and she is a mommy now.

Other items were, pencils, pens, colored pencils, maybe a new pencil holder for the backpack to keep them from going to the bottom some cool folders or notebooks depending on the class needs.
A Disney poncho for rainy days, which was one of her favorite, and a big hit a school.
Lots of little stuff hand sanitizer, lotions, chap stick, burts bee's, clear lip gloss, Hair clips, brush, comb, hair bands. I found some travel size kids products hair detangler, mini sun screen she spent a lot of time in the pool and beach so this was nice when she would stay with friends.
Mittens, Scarves, and matching hat or some fun socks - At Kohls and Pennys they had so really nice ones at a good price. Check the
Disney store online, I have picked up some thing here for stocking stuffer.
Movie GC, or the newest coolest movie
Frozen yogurt place, dairy queen, cold stone whatever ice cream place she likes.
Fast food GC, so if she is with her friends she can take care of herself.
Michaels and Hobby Lobby have some cute little things to put in.