This is the team I used to get to Six Paths. Don't know if it'd class as a spender of f2p...but anyways, here it is:

Sannin Tsunade (with Y+2) - Hirudora Guy - x
Darui - Christmas Sakura - Christmas Tree
x - x - x

Assuming that Guy combos off his standard, it does pretty decent damage, plus two ways of removing Super Armor (Sakura's standard with tree and Hirudora)