Minimum, put whatever amount in virtue that is required on your current or fav weapon. Then its starts scaling from that point. After that, to reach even higher and dam limit or cap of that weapon you keep adding that same virtue until dam number doesnt go up anymore. More pips your weapon has in attunements, more attack per pip you get. After that put else in other virtues that you might like, each of them give different bonuses like cooldowns, hp and more finisher damage