What additional information is given about James Gatz by his father?
The answer to this can be found in Chapter 9.
In my opinion, the most important thing we find out about Gatsby is that he was really ambitious from a young age. We find that out in his copy of Hopalong Cassidy. In that book, we see that young Jimmy Gatz has this schedule that he has all planned out for himself. It is his daily routine that is meant to improve him in various ways. He also has some general resolutions that are meant to improve him morally.
I guess this shows that he was really a better person as a kid because he wanted to get ahead through hard work and he wanted to be a good person -- not just a rich man.
His father brings a list of resolves that Gatsby had as a kid. It was in a copy of the book entitled Hopalong Cassidy. Gatsby's goals were all good, and nothing that demonstrated his eventual "success". He wanted to quit smoking and chewing, read a lot, bathe often, and be good to his parents. He also devoted 2 hours a day to needed inventions.
Putting these things together, I think one could assume that Gatsby was a good ole' American boy looking for a way to make it big... legitimately.
Jay Gatsby was idolized for his success in his father's eyes, but in years of late, he didn't really know his dad at all.