Strategies to complete gold missions of 5,10,15,20
5 - just use your best unit, frontline tank, backline dmg dealer with 1 healer.
10 - just use your best unit, frontline tank, backline dmg dealer with 1 healer. Use Abraham in middle backline to kill enemy frontline first. Use sherry, she will target low hp enemy.
15 - just use your best unit, frontline tank, backline dmg dealer with 1 healer. If have Abraham use at middle backline to stagger Sebastian and Scott
20 - backline R as tanker and stunner, backline Shane for tank and heals, another tank in backline, Abraham for frontline dmg and stagger/group enemy, another healer in frontline.
Note for all stage: remember to make full use of mercenary