Beating Shinra in Ch 5 actually easier than in Ch 3. In Ch 3, you are held to the four coins that you are given, in Ch 5 you can use any coins you have. So you can have like one Quota x4 and beat Shinra easily. Go to the Bikanel Desert and dig, you'll get some decent. Play the people with the Marvelous and Bevelle Core Spheres with a coin that has Rare Coin for some other good coins.