At 31 lvl,you shoudnt spend any coupons or seals.Save coupons,till have 12-14 000,if you impatient,or 20-25 000,if you can.With that amount you can buy ninja like Naruto sage of six path,or Kushina.And spend only when Fukurukumaro deal event is on.That way you will get extra ninja+power items.As for seal scrolls,wait for lvl 70 GNW treasure.