First time marathon runner - what to bring with me?

Hi friends! I’m running my first marathon on Sunday (LA Marathon) and curious what I should bring to the start line. I’m thinking of just bringing my belt with my phone and GUs but wanted to seek any advice otherwise!

They have a bag check you can pick up at the finish line after, but I’ve been told to just bring a jacket to leave there to donate. They’ll have water / electrolyte every mile - so I’m thinking no need to bring my own during the run? 

Appreciate any advice!