to be honest i dont think u need seal scrolls, focus on powering up, save coupons and use them wisely, use ur suns for refines or charms, seal scrolls come by theirselves.

for example for the last 3 months i've spent around 360 on the GNW treasure without even trying to get seals.

go for the power and u can get good ninja from fukurukumaru's deals and make a team around that ninja!
good luck ^^