The rules allow props, but the same advice about using sparingly is good advice. Ensemble dress is traditional. The casts of the first readers theaters wore all black. Many still do. Other teams like a bit more than that.
Vests are popular.
Most students buy their own outfits. At Mt. San Antonio, we budget for ensemble dress. We allow a certain amount for each student. If a cast votes to do more they must pay the difference. The obvious answer is the one you can agree upon.