ChasingSuns
Sage
Personally I don't think that there's a set way to determine how many side characters are appropriate outside of asking yourself what works for the story. I recently bumped into a scenario where there was a scene that I just couldn't get figured out. In the end, I ended up cutting the scene completely. There was a character that would be introduced in the scene, so therefore his appearance was cut as well. I do plan on visiting that location later in the story, but for all I know, that might get cut too. I guess what I'm trying to say is that if a character really isn't helping the story, it will show, in some way or another. You can have a huge cast of characters like GRRM, or you can have a more limited cast. It all depends on the story. If a pet dragon works in your project then go ahead and use it. If not, then don't. But even if the dragon is just there for a sort of animal companion factor, then there can still be purpose to the character. Just gotta do some digging to find what that is. I hope that this helps a little bit