Johnny seems to play an incredibly important role in this novel in terms of representing a good character who is a victim of circumstances beyond his control. When I think of Johnny, I think about his essential goodness in comparison to other greasers in the gang. This is demonstrated of course in numerous ways, but one of them is in Chapter Six when he works out how to resolve the crisis that he and Ponyboy are facing hiding away in a church:
"We're goin' back and turn ourselves in."
This represents a desire of Johnny to resolve the situation and also an acknowledgement that he did do something wrong. He recognises that he and Ponyboy cannot stay in the church for ever, and this is the only way he can see to ensure that Ponyboy is given a future. He hopes that he will receive a lenient sentence, but it is clear he does this sacrificially, knowing that this will give Ponyboy a future.
Secondly, I would want to go to the end of the novel and look at the letter that Johnny writes for Ponyboy and the impact this has on Ponyboy. I think one of the most important things he says is:
You still have a lot of time to make yourself what you want. There's still lots of good in the world.
What is important about this quote is that it signals that the desperate situation that we are presented with in the novel of Socs on one side and Greasers on the other, with no hope of change or escape, is not permanent, and that Ponyboy's future is not set in stone. He can still make something of himself and does not need to suffer the same fate as Johnny. It is this that inspires Ponyboy to record his experiences to try and produce some form of change.