You should collect around 20-30K coupons for Fuku-deals, it can give you decent ninja(s) and a lot of power items, what you will need.

For the SealScrolls: you should collect around 300, and use them when there is a rebate event. You can collect some ninjas from the treasures, and you can get back some scrolls too.

But maybe a more experienced people can give you better advice. ^.^