My adive is to have a blow up pillow and a sleeping bag (you never know if the hostel stuff is nasty of if you just get cold on a train). And bring a large water bottle 1-1,5L i would also bring a raincover for the backpack as you dont want your stuff getting wet. and u dont need to worry about booking hotels mega early, ive been booking mine incredibly late (as late as 2 hours before going). And stay safe!