In trying to practice brevity the only thing I can say is to watch all of DBZ and the material for Goku being ENFJ is there. Their role inadvertently is to protect the Earth and Goku does this without hesitation (Fe); on numerous occasions he expresses his interest being only to find strong opponents (Fe-Se), one of the reasons he spared Vegeta (Fe-Ni). Vegeta on the other hand knew that his only chance of surviving was to go soft, so to speak, and become a good guy. This is all beautifully illustrated when they reach planet Namek and hunt for the dragon balls.
At first he just wanted to prove he was the strongest but then he met Goku, who was somehow stronger or more passionate (he has something to fight for - Fe). Vegeta was discombobulated for being the "prince of all Saiyans" he was, apparently, supposed to be "the one" (Fi) but can't understand how a lower class warrior is actually "the one". Goku beautifully expresses his Fe during the fight with Frieza. He even says something about there being nothing wrong with only trusting feelings, seriously. I'll have to go back through the material and find these sources. The interplay between Nappa and Vegeta is also worthy of examination. His willingness to change lifestyle perhaps suggests weak Si, although there is clearly still some anchoring to the past with him.
ENFJs have Se in the 3rd position and Goku makes excellent use of his, obviously, so it might seem like he's an Se dom. However, his sense of justice is the main motivator for using his Se. His Se is only pushed to limits when mediated by his top Fe. His Ni, mostly hidden in ENFJs, is mainly used during fights. He doesn't only never give up but he manages to find ways to best the opponent. Instead of trying to beat Cell he forfeits the match and suggests Gohan go for it (Fe-Ni?) (*This is also for plot reasons; Toriyama wanted Gohan to become the main character but the fans wanted Goku back, eventually); also throughout the series he communicates plans of attack demonstrating wisdom - someone will try to attack an opponent but he'll stop them and tell them it isn't worth it.
It's a decent series but Toriyama said he doesn't feel it's his best work. It's interesting to note that in Dragon Ball it started off as mystical adventure genre influenced by Chinese lore but in Z, which picks up right after DB ends, 5 years later, it becomes more sci-fi. Toriyama's artwork has always featured machinery and in DB there was the Red Ribbon Army and their androids, but in Z they start going to space before later setting back on Earth and fighting androids and biologically engineered organisms & time traveling, before the Buu saga begins and they once again somewhat revert back to mysticism and magic. Frieza and the Saiyans are introduced as planet hustlers and there's a semi decent amount of astronomy in it. King Kai's planet is tiny but has heavier gravity than Earth, a phenomena worthy of minute amounts of attention. Of course other conditions may be necessary if this were to occur in real life, but the author probably had some fun with it regardless.
If the series ended at the Frieza saga that would have been too soon. Going off the anime, that's a little over 100 episodes, which is maybe what the author wanted. This being a business of course, he was pressured into doing more work which is why later on he started to get lax a bit. Once he couldn't make Gohan the main character is probably when he stopped caring so much. Knowing this, watching the series you can definitely get undertones of Gohan possibly becoming the main character. He couldn't really have done this if the series ended with Frieza, who is only the second antagonist, although some say he is actually the main one in the series.
Even going off that, it is helpful if one watches the less popular Dragon Ball series first, as Z picks up right after it. During the first few episodes and still later there are many references to DB, although they aren't exactly necessary to still enjoy Z. The series would just make more sense to newcomers if they went through DB first before going to Z.
And even with that, it is possible to suggest the series went off track with the third saga, the Android/Cell saga. It may seem out of place, which is why they tried to tie it in with DB's Red Ribbon Army, as Dr. Gero wasn't really a character in DB. I have seen it be suggested that the Cell saga should have been a movie and Brolly should have gotten to be a villain in the series over Cell. A decent proposal as the series would have focused on the Saiyans more rather than the sci-fi aspect. Brolly, though, while kind of lame, would have given the series an entirely different feel, if not a repetitive one, than the new age tone Cell brought. Vegeta wasn't really supposed to be a main character but he received lots of fanfare and so was brought on. The series was then given a new Saiyan character with Trunks (over Brolly), who had to show the progress these characters were making by easily defeating the previous villain Frieza and his more powerful father (Frieza, by the way, in his final form is designed as an alien. In his first forms along with Captain Ginyu, they resemble devils). Some also suggest, rather than the Cell saga, Cooler should have gotten more spotlight. This is still more rehash. The series, beginning with DB, was not intent on highlighting the Saiyan race. Even the Super Saiyan was created only so the assistant wouldn't have to use so much ink on the characters's hair. So with this third arc possibly being the last, the group needed a super powerful opponent to end with. Honestly, who knows where they got the idea for the Cell saga from? We needed a powerful enough villain to show that Gohan is now the main character, the torch having been passed.
A theme constantly revisited throughout the series. Even in the final saga, Gohan in his mystic form is not enough, after we see Goku struggle to save the day. So we are then introduced to Gotenks, who turns out to not be enough either, as the series, pressured by fans and politics, temporarily does away with its proposed theme and goes back to Goku saving the day again. It is clear why the final saga gets disapproval from many fans, who claim it does the entire series injustice. The series then is about a man and his family. Goku will always be there to save the day!
It should also be noted that, again while the series was "supposed" to end with the third saga and Gohan now being the savior of the Earth as his father finally passes away, Toriyama was pressured into nearly undoing that by being forced to do another chapter, to please the raving fans. The anime was only ahead of the manga by a little bit, so they were kind of winging it, which is why Vegeta was decided to be a staple character as well as the creation of the Saiyan race. It is unclear how much of the story was planned and how much improvised. The Frieza saga being the show's end makes some sort of sense, but the series ending one more saga after Frieza's makes more sense.