You need to think about what you want to do with your CYOA. Is it a power fantasy? A waifu builder/picker? An adventure? Guided worldbuilding? A writing prompt?
Each of these categories have different characteristics.
If you're trying to make a power fantasy, you should focus on having cool shit to buy and be mindful of synergies. The setting is not that essential here, aside as a gauge to your own power.
If you're trying to make a waifu builder/picker, first you should focus on a theme (a more generic one runs the risk of being too impersonal to be of any interest). Don't underestimate the importance of the psychological aspect, but the physical is generally the protagonist.
If you're trying to make an adventure, detail is important. Background, ties with the existing powers, connections to the mythos of the world, setting-specific equipment, companions, and of course quests.
If you're trying to make a CYOA based on worldbuilding (like a city builder) the process that brought the world to its current position is the protagonist. Why is that city floating? Magic? Or lost technology? How did it came to be and why?
General advice: Keep the text as clear as possible, no elaborate backgrounds for the text-boxes, space long paragraphs so that the eyes can take a breather, use if possible justified text and with a comprehensible font. Titles are of course an exception to this and can be quite elaborate, especially the main title.
Try to keep your art consistent; don't stress yourself too much if some pics don't fit perfectly, but do consider alternatives, even if they are slightly less expressive.
I'll post more if something else comes up to my mind.