Few series do training bows as well as dragon ball. From first to last, Akira Toriyama never approaches her training arcs in the same way. There are similar concepts, of course, but the way it approaches character training changes dramatically as Dragon Ball enters its twilight years.
As is the case with most Dragon Balls, training bows are extremely inconsistent in quality. Some are near-genius works, which develop Goku considerably in the process. Others are mostly just helpful, pushing the story forward in a fun way. Regardless of how a training arc unfolds, they almost always mark a time to reflect on the characters and themes of the series.
10 Trunks trains with Vegeta
There is a deliberate lack of attention to the time Vegeta and Trunks spend together in the Spirit and Time Room. Toriyama wants readers to ask themselves what has developed between them over the course of a year. After all, their dynamics are noticeably different, albeit only slightly in the beginning.
That said, while this creates intrigue, it's not a particularly compelling training arc. Interestingly, the anime actually adds a flashback scene to their training. Of course, it's about Vegeta that spin
9 Grounders train for Saiyans
This is a training session that mostly happens in the background for both versions of Dragon Ball Z. The manga does not even devote an entire chapter to training Grounders. Instead, almost everything is flown over in a series of panels. The anime features at least one episode that mainly involves Grounders preparing for the Saiyans.
That said, the fact that Grounders train so mildly ends up actively contributing to the tonal shift when Yamcha dies. The Grounders prepared as if the Saiyans were another battle. But they are not martial artists, they are murderers. That's a surprisingly good reward for such a disappointing training session.
8Gohan trains with the Z sword
Dragon Ball is at its best when it's fun. Akira Toriyama uses humor incredibly well. The comedic tempos in the series very rarely feel tonally out of place. Needless to say, Gohan's time-based training with the Z-Sword has a significant amount of appeal. It is played as a typical training session until Gohan breaks the blade in two.
From there, a Kaioshin Roshiesque medics with Gohan for a whole day while also reading adult magazines. This is not to mention that Goku tries to use Bulma as a tool to hit the Rou Kaioshin to empower Gohan. It is played primarily for laughter in typical dragon ball fashion, but it also lacks the drama that the series typically uses well.
7Goku trains with Popo and Kami
Interestingly, the Demon King Piccolo's arc does not end with Piccolo's death. Rather, he goes on for a while longer, building and tackling Goku's training with both Mr. Popo and Kami, God himself. While the build-up is handled very carefully and a significant amount of care is given, the training itself is on the boring side.
Popo and Kami are both very interesting figures, and what they have to teach Goku is fascinating, but there is no real meat to chew. Toriyama doesn't really go beyond the surface level with this training arc. It is not until the 23rd Tenkaichi Budokai that Goku's training with Kami is further deepened.
6Gohan trains with Goku
What makes Gohan's training session with Goku in the spirit and time room so good is not the training itself, but how Toriyama frames it. When viewed as it is, the arch doesn't really offer much to be excited about. But when paired with the moments that Toriyama chooses to reduce, the training arc receives more depth.
It is also Toriyama's way of creating tension. While Goku tells Gohan about the drawbacks of overcoming Super Saiyan Grade 2, Trunks and Vegeta are at the end of a Perfect Cell-related beating because they haven't perfected their versions of the Super Saiyan well enough. It is used convincingly. Plus, it's just great to see Goku and Gohan interact so intimately.
5Goku's trains on the way to Namek
dragon ball between Raditz's arrival on Earth and Goku's arrival on Namek is a very interesting time. Aliens are still a new concept, Namek is still foreign, and Toriyama's world-building has expanded to a galactic level. Goku is also probably the most interesting here. It goes without saying that his training arc on the way to Namek ends up being thrilling.
Goku realizing the benefits of his Zenkai ends up pleasantly countering the fact that Vegeta has to make use of what we can find on Namek. It's a very controlled training session for Goku too, almost professional. The bow is Goku actively preparing for Namek in the solitude of space. What's wrong?
4Goku trains with Kaio
There was a time when the death in the dragon sphere carried considerable weight. Goku dying so quickly in the Saiyan arc has a major impact even as he remains in the spotlight of history. For the moment, Goku is truly dead. And in typical Goku style, he left to train with a new master.
Kaio himself is a fairly entertaining character, not unlike a tamer Roshi, and helps expand the dragon's sphere reach over the world considerably. It also marks the last time Goku has a martial arts master who trains him for a considerable amount of time. Goku spends a number of chapters and episodes with Kaio, but it's all handled exceptionally well.
3Gohan trains with Piccolo
While Goku's time with Kaio is fantastic, it's completely overshadowed by Gohan's training under Piccolo. As for training bows, this is the most dynamic of all Dragon Ball. For the first half, Gohan is alone as Piccolo watches him from afar. Gohan is forced to survive alone, adapting to the world around him.
The second half sees Piccolo and Gohan training together, slowly building their relationship. It's amazing how much growth Toriyama can convey in just one panel. When the Saiyans arrive, Gohan and Piccolo are fundamentally different characters, and that's all because they trained together.
2 Goku and Krillin train with Roshi
There really is nothing better than the classic. The first training arc of the series, before the start of the 21st Tenkaichi Budokai tournament, sees Goku training with Roshi. In the process, two new characters are added to the cast: Goku's new rival, Krillin, and Roshi's new roommate, Lunch. While the latter is a bit bland, Krillin ends up playing a huge role in the rest of the series.
Goku and Krillin become best friends as they learn everything Roshi has to teach them. Better yet, the Turtle School philosophy is genuinely ingrained, giving Roshi a lot of depth and dragon ball a sense of legitimacy when it comes to her depiction of martial arts. At least philosophically.
1 Goku trains with Karin
Goku's training arc with Karin (or Korin in the English dub) is deceptively short, but it's incredibly important. It's a training session intimately linked to Goku's first big loss via Tao Pai Pai, Goku's flaws as a martial artist, and how Dragon Ball approaches martial arts. With Karin, Toriyama adds a layer of divinity to the art of combat.
Better yet, Goku's training is so specific that it's much easier to engage with the process. Karin wants Goku to think before acting. Within days, Goku learns how to outsmart his opponents, allowing him to take revenge on Tao Pai Pai. Rarely is Dragon Ball so concentrated.