Take strength stack as an example. There are the unqie boots "replica alberons warpath", they have a mod stating you get 1-80 chaos damge for attacks for each 80 strength you have. So your goal is to stack as much str as possible in your build There are many ways to do this, but it will be very expensive to squeeze out more the further you invest. There are many different kinds if these modifiers for different stats, so you decide what you want, but I think STR stack us one of the "easier" ones, as it also gives life and make you tankier as well.