Balanced Combat System?

I was wondering how to make a balanced combat system.

I have heard of the method called “leaky bucket” but I’m not sure how to go about this.

In my game, I have magic attacks that can vary from being ranged or up close, I have melee attacks that can be ranged and up close as well…

I’m not sure how hit stunning works, I’m not sure how perfect blocking works. Any help would be greatly appriciated!

( I’m not looking for a full script, just some examples with explanations )

From a quick search I found an explanation of ‘leaky bucket’ which may help.