Encyclopedia of my world

I've been thinking on making a journal-type encyclopedia of my world, like the journal of an explorer who travelled the world and learned about it, and then his or her journal became an academic book used in schools in the whole world. However, I don't know where to start or what should be the order of the topics in the journal.

For example, should I put a chapter for history first? For religion? Or should it be about geography?

What do you recommend me? Where should I start? Do you have a template of some kind?