Using google docs, since it’s your first go, is probably the right move. Use a font for the main text that is easy to read. These will usually have round glyphs like futura, poppins, or IBM Plex. Use condensed fonts for tables, like Oswald or IBM Plex Condensed. Use a fun font for headings that matches your adventure vibe. Putting stuff in two columns will increase readability. And lastly, write your content such that you reduce page flipping. You’ll be off to the races!
For further reading, check this out: https://www.drivethrurpg.com/en/product/168306/A-Brief-Study-of-TSR-Book-Design?manufacturers_id=3482