Wow serious backpacker hu, that's cool!
I'm just more of a day hiker. I usually carry a day pack with 3 bottles of water, four at the most, a bottle of gatorade and some extra food.
I recently went on my own solo camping trip a few weeks ago so I got extra gear such as a whistle and compass as well as a small but durable flashlight and batteries.
My camera and a notepad and pen are always a must for me since I'm one of those types that likes to reflect on things.
And always some first aid kit things since I'm prone to triping a lot on trails
One time my dad and I went hiking and I must have fallen at least 3 times or more.