The things to carry with you on trip will depend on the type of trip and many more factors like
1. Place - Is it a beach, mountain, site of historical importance 2. Weather
3. Type of transport you are going to use while commuting 4. Number of days 5. Your fitness
There are many more such things. But one thing you should always carry is the basic medical kit. even if you don't use it, it might help someone else.
Keep in mind what the people of that place do not like and then avoid that, also check the prices of everything so that you're not cheated. Otherwise carry a pepper spray, maps, power bank, sun block, a bottle of water, and if travelling abroad, some translation tools