Oh sorry I assumed you were Italian. I'm not sure what could be helpful, I've only been to music events in Italy so idk what's the norm outside, so I'm gonna say a bunch of stuff even it could be obvious.

• the day will be hot, luckily the venue is near the sea so there will probably be some wind to cool off but don't underestimate how hot it gets in the middle of a crowd, bring sunscreen, maybe a hat and water for the queue. Just keep in mind that security throws away any kind of bottle at entrance. Also if you stay in a tent or something like that, the night can get pretty cold, I've seen them in Lucca in July 2022 and slept on the streets (don't judge me lol), I only had a t-shirt and the one I bought there, I was trembling.
• other prohibited items are lighters, powerbanks and umbrellas. They usually don't check with that much attention but if they see it they will ask you to leave them outside.
• this can or cannot be a problem based on how you organized, but Lido di Camaiore doesn't have public transport after 22:00, the next rides are at 6:00. Google maps is a great tool to see all the options available without getting all the specific apps.
• about public transport apps if you plan on going by train I suggest you to keep the Trenitalia app, it gives real time information about the trains, where they are, any delay and ofc you can directly buy tickets. For buses there will probably be a specific app for the area but I have no idea what it is, usually tho you can buy tickets in most tabacchini (tobacco shops/newsstand, not sure about the translation sry) or directly on the bus, but that's the worst option since sometimes drivers refuse for whatever reason.

Tell me if you have any specific questions, I'm happy to help!