A must since you never know when you will need a towel and most hostels make you rent one and full size is to big
A must for charging anything any place!
Get good hiking boots and make sure to wear them in before you do lots of hiking!
It rains every place, get a small one that folds up into a bag
A must have if you do any hiking especially off trail
Wool socks are a must! They keep your feet warm absorb extra sweat and dry quickly!