http://rerollcalculator.com/go there. put in your weapon stats, then decide on what to roll to give you the best damage outcome.
ie, should you roll min/max or %dmg. dont know which one would give you the most dmg?
use the calculator. way better and you wont waste mats trying to get something perf, when in the end, you might have gotten better dmg rolling the opposite of what you did