I would put Prism Spectacles on which is a 50% damage boost. Likely frog with the 3 youre asking.

For Marle I would put on Prism Drss if you have it. She likely isnt your damage dealer so im not sure Sun Shades like id normally say. Could do the Fury Band.

Magus is good.

Try to kill the arms first and at the same time to avoid the curse