
I'll start. I think that each character is every bit important to the Naruto manga storyline.
I think Tsunade has become a wonderful mentor to Sakura. She is really like a grandparent to Naruto, giving him a real sense of family. She believes in him, and almost requires Naruto to be on most missions of upper ranks.
Then there's Jiraiya. I'm not going to give any spoilers, but I really have gotten attached to his comedic habits. He builds a strong relationship between him and Naruto that Naruto can be proud of. There are soo many more techniques to be learned.
Finally, Orochimaru... most people despise him, but I cannot think of a more curious villian. I think his darkness and secrets are interesting. I would like to learn more about his parents, and the psychology of his ways. Moreso, how does Sasuke put up with him, and how do they trust each other. How strong is their bond?
Overall, the manga has been focused on the Akatsuki for those who love evil, but I am curious to watch future episodes that include the Sanins.