F2P, best way to maximize your resources is to save up specific amounts to get more of what you're gonna spend .. For Seal Scrolls, it is highly recommended to save up to 264 Seal Scrolls for you to reach 300 Rebate Tier ..

10 Seals = 1 Seal Rebate

50 Seals = 5 Seal Rebate

100 Seals = 10 Seal Rebate

200 Seals = 20 Seal Rebate

--- 36 Seals from Rebate + 64 remaining Seal Scrolls from your savings = 300 Rebate Tier Accomplishment which will give you 30 rebate seal scrolls for your start-up for new batch of saving for the next Seal Rebate ..

Now for the treasures, what's better is to only use Seal Scrolls on GNW Treasure and Kage Treasure .. Kage Treasure houses the Barrier Ninjas that you will need in game, aside from that, other ninjas from that treasure is not that great to use in your main team but useful enough for you to survive your early gaming phase .. GNW Treasure also have great ninjas to use such as Kushimaru, Jinpachi and Sasori which is also used by current teams this days (Edo Hiruzen Teams with Sasori, Edo Deidara Teams with Jinpachi, etc) .. Other Treasures, just leave it and just free draw from it, you will eventually get the Super Rares of that Treasures .. Focus on 1 treasure also if its possible so you will get your Super Rare faster ..