How do Active Abilities work? Do you ever get a strat line options to say use one over others?

What determines when your gladiator will use them?

Does higher ranks in the talent increase your odds of doing it? Or how often you do it? Or both?

I'd love for more information. Is it bad to pick up all the basic abilities at 1? Or does that just confuse your gladiator so he does not know which ability to use?