- Passport and other form of ID
- A couple credit cards (different banks, without foreign transaction fees if possible)
- Cell phone and charger
- A daypack/backpack, around 30l max unless you are carrying backpacking gear (I've used a cheap backpack from Walmart to travel the world before and those wear just fine)
- Change of clothes (they don't need to be ExOfficio or anything like that; stuff from the Goodwill is fine)
- Toiletries/first aid stuff in a ziploc bag
That's literally all you need. Bring some snacks and a bottle of water and you are set. Any other stuff you bring should be carefully considered as you can usually find anything else you need on the road as you travel and traveling lighter is always traveling better.