Hank of Runehammer always has one DM journal where he creates content and journals his DM’ing notes and session prep (only prep the next session). He showed off Sword Fish Island’s emptish DM book. Worldbuilder's Notebook (Red)
Each colored notebook has a different color end page artwork.
I have used Moleskin empty notebooks for DM journals, empty grid notebooks, and for my brother’s one-on-one Planar Compass game, I am using a SwordFish Island Worldbuilder’s notebook (black).
I have and I think it’s very beneficial but my discipline wavers. One thing I enjoy about streaming my session recaps (when I manage to!) is that it really forces me to write down notes better than I might if left to my own devices. I think a public DM diary serves a similar purpose in that regard.
I wanted you to check out the Sword Fish Island Worldbuilder’s notebook because it has hex grids, hex flowers, and dotted pages. And at the back, maps, random tables, and finally, a section on random dice probabilities, which might be helpful. My personal goal is to use the hex maps to build an arbitrary prime material plane and outer plane map.