That depends, each one of them does different things. Block and Armour Penetration for example are activated effects, i.e. they do nothing if they don't trigger. Extra Armour/Critical/Damage/etc. ranks are passive, they apply to every hit delivered or received. The Kill and Life Protection ranks are checked at the end of the fight, successful rolls result in a bonus kill (which probably wouldn't happen otherwise) or one less invoice from the Temple.

As for the values... it depends again. My experience with the activated "ranks" is that you need at least 100/1000 to seem them triggering once every few fights of medium length. At 200/1000 they trigger nearly once per fight and 300/1000 makes them a fairly common sight. Of course, if you're lucky, you may get 2-3 triggers per fight even for 100/1000 but that's unlikely. The passive ones are harder to judge as you don't see their direct effect but rather gain some general idea if, say, the damage or your gladiator goes up or not. Wars should benefit the most from the Extra Armour ranks while Rages - from the Extra Damage rank. So far nobody has really tried increasing these ranks above 200-250 or so, the investment in attributes seems to give better results all around.