At this point getting seals take forever especially if you are full f2p. I think it is good to do 210 on limited time treasure to get edo roshi, then everytime you have 300 do the GNW treasure. The season ninjas are not half bad and better then most rares in the tresures. If you aim for legendary from the treasures it will take years to get the 1000-2000 seal scrolls needed