Rebate applies to Edo, Jinchuuriki 1 and kage treasures. If you will pull from jinchu2 for han or sage for naruto, you won't get any seals from rebate. Since you're not even considering edo, your only rebate-related option is Kage. Now think if you really need more ninjas from kage (you have 4, so now you have 50% for both a duplicate and a ninja you dont have yet). If you decide yes, then pull for 300 to get last 30 scrolls. If you dont, then pull 10 into kage anyway to claim additional 20 seals and stop there.