>>545699871
For example, here is three random thieves
>Bakesh: Treasure Trap Detection - amazing skill you want on your thief
>Amelia: Stealth - great skill you want on as many units as possible
>Milana: Poison attack - useless trash skill
Out of these three, you would put Milana in your main party and level her discipline. If you used either of the other two, you would not have extra copies to use for discipline.