What is a normal breaker size ? And how many runs can you have off one breaker ?

I will assume "normal" means typical. Most circuits can be general purpose lighting circuits, and can be either 15 or 20 amps. Small appliance circuits are always 20 amp. Major appliance circuits can be either 30, 40 or 50 amps.

Not sure if this helps you or answers your question. Why do you ask?

What do you mean by "runs"?