I'm a f2p and this is my current line up which work quite well so far
Note:
If u don't have Kabuto and Sasuke 3* yet, u c*e Kakashi and Karin insted
Start with Rasengan to activate hinta chase skills and Kakashi chase will follow after

At the moment wind main is the weakest character or "*" as some ppl said due to her low growth stats so don't be disapponted if u end up losing to others (more likely Fire and Lightning cuz they are so dominant atm)