This game is like a deckbuilding card game. You're constantly going to have to make teams in this game for future challenges as the meta and events shift. You need to learn how to build a good team now while you have a chance to understand the core concepts, before all the crazy ninja arrive.
Rather than ask for teams, look at the teams of other players and try to understand why those teams work and why they selected certain ninja. *yzing the comps of others is a good way to learn how to play so you can build your own effective comps. After all, you can't upgrade every ninja. You're going to have to make choices about who to keep and who is *. For that you need to understand the game.