Don't spend on Iruka or Sailor, only spend on Sailor if you want to run disgusting cancer teams. The only ninjas worth spending on are - Jonin Minato, Obito (Masked Man), R. Deidara, Ay (3rd Raikage but if you are f2p best to wait and just draw him I guess), Roshi, Kushina, Killer Bee (normal) Cursed Hidan (questionable - i'd say probably not worth it), Tsunade 5th Hokage (questionable - i'd also say still not worth it)

I'd say wait for lucky dice to come back with one of those ninjas you want or preferably the summer break outfit in Lucky Dice as that wa sonly 5k total, it's more expensive this week and the chance for Tsunade or Tendo frags doesn't make it worthwhile