Benjamin U 

Because they are normal middleschool kids, useing items from your closet can save money and make it more believable. Goodwill also has many amazing options that are cheeper. 

Pants- Baggy jeans and long jean shorts were popular. 

Tops- Wearing multiple shirts at once was in style, lots of layering (think T-shirts over long sleeve shirts). Because shirts with pictures or words can make the stage seem a bit busy stick with plain colors or shirts with minimal designs. (Graphic tees were popular but for the sake of the show just stay away from them.)

Shoes- just use something they feel comfortable dancing and moving around in. Stay away from shoes that can slip off feet easily, like flip-flops, crocs, or sandals.

Accessories- Necklaces, simple bracelets.