I'll start.
1. I spent about 3-4 days since I only found the jam 6 days before the end. I created 2 in that time span.
2. Make sure you consider how strong your colors are and how readable your text is. It will prevent eyestrains and confusion.
3. My main challenge was fitting everything into one page. Sometimes, I had too much. At some point, my wording could be too convoluted. Other times, I feel like I used too many words to explain simple concepts
4. I can recommend Loco-Motion as an underrated game. It's pretty simple and quick to play, but the possible expansion and journaling capabilities sells it for me.