Hi, I'm traveling by myself in the Balkans for 34 days next year in the summer, I already made a basic itinerary on which countries I want to travel through, Romania, Serbia, Montenegro and Croatia.

My question is, I'm traveling with just a backpack and the clothes on my back, what should I pack in my travel pack? It'll be with me at all times unless I stay at a cheap hotel where I can leave it for the day.
My backpack is a 5.11 Tactical Rush 72hr backpack.

FYI, I've never traveled before, so I figuered this forum would be a great place to ask newbie questions on how to pack my travelpack correctly.