Always bring a hat, sunscreen, water (1.5 L minimum) and groceries (fruit, sandwiches, candy) and a telephone for emergency situations.
Camera, notepad, some money, maps, GPS and binoculars, are also useful.
A first aid kit with plasters, bandages, disinfectant, foot and knee elastic is also important to bring with you.
Make an effort not to carry anything superfluous, the weight of the backpack is decisive for the comfort of the hiker, especially after the first kilometers.