This is a nice guide, as far as telling newcomers who to expect in the 60 and 70 treasures, but not much after that.

Spend your Seal Scrolls in any way you want, just keep in mind that you probably won't get a rare until the 60 mark, and you'll probably never get a Super Rare lol.

If you want one of the Pains, screw Sage Naruto and pull for the Pains. If you want that Asuma Wind Blade, then cut your losses and pull there.
Pull for what you want to pull.

Of course, if you want Sage Naruto, Ao, or Orochimaru, then the above actually applies. Save up and spend it all in the 70 Sage Treasure.

In the long run, you'll get the same amount of Rares, just different characters depending on what you pulled on.