• uniform
• trainers
• spikes with extra 1/8" needles
• warm-up clothes (wear over uniform)
• water bottle
• extra socks
• change of clothes (bring layers)

Nice to have:

• healthy snacks and/or money for concession stand
  
• chair
• blanket, pillow
• homework, book to read
• cards, games
• music and earbuds
• deodorant, other toiletries