Well depend if you cheat or not. If you cheat and up your stats then whatever you do you win.I really do not understand the combat, can someone explain? Or show an example of how
If not; First know that Agility and Strength increase the physical damage you deal. For dealing damage upgrading agility is better. And gladius takes both Strength and Agility into account so it's the better choice.
Strength upgrades your grappling game.
Stamina upgrades your stamina and reduces your damage taken.
For the moves I'd recommend maxing 'Assault'
With high agility the damage it deals is insane.
And dunno why but when you use assault; if you have higher agility than your opponent it automatically parries their attack and you take no damage.