Just getting a 2 star Iruka is not really recommended. Especially if you're a F2P like me. It's so hard to do ninja exams with just a 2 star iruka. Would recommend to have it at least 3 stars.

Edit: Yes you can pass all ninja exams with just a 2 star iruka. But it's gonna be hard and you'll rage so many times when iruka just die so quickly.