I beat Shinra on my first try when I had a game against him in Chapter 3's Sphere Break tournament. Maybe I got lucky, I don't know. I can't remember what it was called that I used since it's been so long since I played the game, maybe "2 coin echo"? I first put the initial coin from the center and then two from the borders, and I kept doing that until I won. I think he put a 1 coin a few times. I reached the quota on my 2nd last turn... 14th, I think.