Of course, this is rather a subjective question, as what may strike me as being important may not be the same for you, but here goes anyway. I will supply page numbers, but bear in mind your edition of this classic might be slightly different from mine, so the page numbers may not correlate.
The first quote I think of as being important is Walt's reflection on his son and his excellence:
"Chris was good at almost everything he tried," Walt reflects, "which made him supremely overconfident. If you attempted to talk him out of something, he wouldn't argue. He'd just nod politely and then do exactly what he wanted."
This is interesting in terms of helping us to understand why so many people failed in trying to counsel Chris to be more cautious and why Chris himself insisted on going to Alaska anyway.
I think another revelation about Chris's character is given to us by the author who points towards the darker side of his personality:
Many aspects of Chris's personality baffled his parents. He could be generous and caring to a fault, but he had a darker side as well, characterised by monomania, impatience, and unwavering self-absorption, qualities that seemed to intensify through his college years.
This points towards the more selfish, darker aspects of Chris's character that indicate the way that he was able to shun people and civilisation and act in rather selfish ways, foreshadowing his retreat from society.