Yo, save all your scrolls for kage/jinchuriki.

I think you c*e your first 10 to pull something from seal treasure, otherwise just keep saving.

It won't be a problem at this stage to use up all your seals/coupons, 8 days isn't too long a time.

Just save them until something good comes out, maybe Hidan 2.0/Sailor Sakura?

It's worth spending some coupons to get 3 star Iruka, but keep in mind as you get more 5 star ninja, you will eventually get free Iruka frags from refining fragments.

Keep doing elite instances of Sasuke. Since much stronger Sakuras come out during the game (GNW/Sailor), I wouldn't see the need to farm her, imo. Same applies to Naruto, but I suggest you get all of team 7 to at least 3 stars.

Get Hinata or Kabuto as soon as possible. They will make your team slightly tankier during fights compared to other teams. For plot and elite instances, just run the team 7 combo.

Hope that helps, if you have more questions you can message me instead, since I can't check if you replied here.