When Kenny first meets Rufus, he thinks that Rufus will be his "personal saver" because he predicts that the kids at school will now tease Rufus instead of him.
Kenny does not quite fit in at school, and is frequently the object of childish torment and ridicule. There are two reasons, as far as he can see, why the other kids give him a hard time. The first is because he has a "lazy eye", and the second is because he likes to read, and the teachers think he is "real smart". Naturally, these things do not endear him to his peers.
When Rufus comes to school, Kenny notices with a sense of glee that the new boy is even more of a misfit than he is. Rufus, like Kenny, has at least "two things wrong with him". The first is his "country" accent and manners, and the second is the obvious shabbiness of his clothes. Kenny's first thought upon meeting Rufus is that now, the other kids will be so busy making Rufus's life miserable, they will leave Kenny alone.
Kenny's use of the term "personal saver" is a slightly inaccurate allusion to Jesus Christ, whom he has learned about in Sunday school. He knows that, to those who accept him, Jesus will be a "personal Savior", who is "sent by God to protect you and to help you out". Even though Rufus doesn't "have a beard and long hair and...wasn't born under a star" like the Son of God, Kenny is convinced that he has been sent by God to make his life better (Chapter 2).