Looking for advice for formatting, etc.

Hello everyone! Thanks for looking at my post. I’ve been working on a story for kids for the last few years and I’m finally at a point where I’m thinking about actually putting it out. I’m still in the refining stage, but now I’m also starting illustrations and such. Im curious as to if there is a standard size folks usually use for different types of books. I’m not sure which age bracket my story is appropriate for either. It has 8 chapters and will have 2 or 3 illustrations per chapter. It deals with some semi-heavy topics. Kids being mean and stuff. So mostly I’m curious about formatting and sizes, I guess. Getting it published is a long shot so I’ll probably be doing it myself. Any idea where to do a full color book that’s ok quality but also won’t crush me financially? How many should be printed for a first run?