Just your band folder or binder to keep band and private lessons materials together, or
One inch 3-ring binder with pockets on inside of front and back cover and top loading sheet protectors just for lessons. Your method books will fit in binder pockets, or
Separate band folders/binders for school band and private lessons
Metronome and Tuner:
Tonal Energy App ($3.99 for Apple and Android) for your phone or tablet. Or...