There are quite a few meta ninjas that a f2p can get. madara edo full bt, Jiraiya toad chant, Itachi edo full bt, sai suit bt, Tobirama NY, Hashirama Ny Bt and hopefully you can try to get Orochi gnw in some 60k fuku deal, however it's very scarce.

Regarding your 3-star Itachi [Edo Tensei] and 4-star Kakuzu [Earth Grudge], while they may not be as powerful as some of the newer characters, it's important to consider their potential when combined with other units and the synergy they can bring to a team.

To determine the strongest lineup in the game at the moment, it's advisable to stay updated on the game's community, forums, or official channels where players share strategies, tier lists, and recommendations based on the current meta. These sources can provide valuable insights into popular and effective team compositions.

Additionally, exploring in-game resources such as character descriptions, abilities, and stats can help you understand the strengths and weaknesses of different units, allowing you to build a lineup that suits your playstyle and preferences.

Remember, the game's meta and balance can change over time, so it's always a good idea to keep up with the community and stay informed about updates and changes made to the game.

Enjoy rediscovering the game and have fun building a powerful lineup!