Day 2 of the 3D2Y Sanji grind, and I've managed to increase my clear rate to ~80% success, using the same team as before. The key for my team is to go into the boss stage with Marco 1-2 turns away from his special, and let it rip at a critical movement while I dedicate 1-2 turns to getting Indigo to ~60% HP.
At that point, pull the trigger on Arm Point Chopper, 3D2Y Sanji, and Arlong's special and go for the burst on Indigo. If I don't KO him then and there, run over. If I do, I've won as I can usually kill the gorilla with ease using the Friend Captain Sanji's special once I've got a good orb lineup. And worst-case scenario, GP Usopp is usually ready to go for the second stall on the gorilla.
So far, 9 Sanji books. The nice thing about it is that I'm also getting 3D2Y Chopper and Kohza books, whom I both have. The only bad thing is that I'm running through gems like water, 100 box space in two days.
What's the ideal ratio of books per special up to target for boosted skill up events? I ideally wanna get my 3D2Y Sanji's special banked before Dr. Indigo is gone.