By F2P i mean ninjas that are some what easly acquirable (not from treasure ).
What i found to be "the best" would be Sasuke , karin(or kabuto) and hinata. they are easy to acquire and are doinf a pretty good job.
Another F2P team the Cursed Seal team(kimimaro jugo and sasuke) this one is good but not as good as the previous one.
If you know other F2P teams let me know. :)