Ash chose Vermilion Gym as his third gym mainly because of its proximity, and also because of its difficulty.
Kanto's most famous gyms are four: Saffron, Viridian, Cinnabar, and Fuchsia. According to Brock, these are truly over-the-top.
Even at the lowest difficulty, they're not something Ash can handle at the moment.
Besides these four gyms, the most suitable ones to visit are Vermilion and Celadon.
Celadon City is a bit far from where they are, and whether they go directly to Celadon City or detour through Vermilion City adds less than a week's time.
The difficulty of these two gyms is similar. The Celadon Gym specializes in Grass Type Pokémon, while Vermilion Gym specializes in Electric Type Pokémon. In terms of attributes, the Celadon Gym might be slightly easier to challenge.
After all, Ash has two Pokémon that can counter Grass Types: Flying Type and Bug Type Pokémon.
But the more badges, the greater the challenge difficulty. Putting aside the journey, if they first challenge and smoothly pass the Celadon Gym, coming back to challenge Vermilion Gym will increase the difficulty.
Originally, between the two gyms, Vermilion was already more difficult than Celadon; if the difficulty increases even more, wouldn't that be asking for trouble?
Therefore, even without considering the journey, it's more advantageous to go to Vermilion Gym first since the difficulty is lower.
To reach Vermilion City, they need to pass through many small towns. In terms of journey, this might be their longest journey so far.
...
Time flew by, and a week had passed. During these seven days, Ash and his friends only passed through one small town,
resupplied with some daily necessities, and then hit the road again.
Along the way, Ash encountered many trainers on the roadside, but he didn't lose a single match. Each night, he would review and correct mistakes in the group, as the experienced members pointed out a multitude of shortcomings. Without their guidance, he might have started looking down on others.
The continuous victories brought not only the thrill of victory but also an inner pride. For a fifteen-year-old, not feeling any arrogance after not losing a single match since debuting speaks volumes about the mentors in the group.
After experiencing the higher realms of the world, how could Ash take pride in such minor achievements?
Especially when everyone in the group had achieved success in various domains in different worlds. Compared to them, his level of victory was just an insignificant step in their growth pathways.
This is why Ash hasn't become arrogant yet. Misty and Brock, who initially wanted to knock some sense into Ash during the journey, were quite surprised.
A rookie trainer met with almost no obstacles and won battle after battle. He obtained two Gym Badges without losing a single wild battle, yet he hadn't grown any sense of hubris.
In terms of mindset or Pokémon battle strategies, these are things a newbie trainer typically can't achieve!
The two naturally attributed Ash's current performance to Professor Oak. As the former Kanto Champion, it's not surprising he has such nurturing capabilities, right?
On the journey, Misty also inquired about "Zippy Zap" and the reason for Pikachu wearing a cap. Despite only wearing a cap, Misty, being a Gym Trainer, could tell that Pikachu's strength increased in that state!
For an Advanced Level Pokémon to leap towards battling an Elite Peak Pokémon, it can't just rely on attributes and skills.
Without enhancement, achieving such a feat is akin to daydreaming.
Ash hid the truth about Pikachu's companion form, saying only that he and Pikachu could merge their Aura, allowing Pikachu to gain some of Ash's power. This was the reason for Pikachu's increased strength.
As for Zippy Zap, it was a move Pikachu came up with a flash of insight after wearing his cap. This skill can only be used while wearing the cap, which is why it needs to be worn on Pikachu's head.
Misty curiously took Ash's cap and tried it on, resulting in nothing happening.
Brock also finally solved a mystery: how Pikachu could use a skill like Aura Sphere that had never been seen before. It wasn't Pikachu using Aura Sphere, but Ash!
Even as a Gym Trainer, it was his first time hearing that a trainer could share some of their capabilities with their Pokémon during battles...
For ordinary people, having such sharing power is useless, as trainers are just humans. How can humans be compared to Pokémon?
But Ash isn't just any human... More precisely, his physical constitution and his unique power make him almost non-human. In real duels, even Elite Level Pokémon might not be able to defeat Ash directly.
In this short time, Brock and Misty have begun to understand Ash's strength, although their understanding is still quite superficial...
During the week, all of Ash's Pokémon had made improvements to various extents. After all, battling against roadside trainers while traveling and occasionally sparring with Brock and Misty had to lead to growth.
Pikachu reached Advanced Level, learning several new skills.
Butterfree and Pidgeotto reached Advanced Junior Level, learning some skills as well, though Butterfree still hasn't learned the crucial Enhancement Skill - Tailwind.
But for now, Ash's current skill set is enough to cleverly distress his opponents.
Lastly, the little Ralts reached an impressive Ordinary Intermediate Level.
Though level-up speed is faster at lower levels, jumping from Newbie Level to ordinary intermediate in seven days without any evolutionary power-ups was already extraordinary!
The reason Caterpie could leap from Newbie Intermediate to Ordinary Peak in seven days was due to the Power of Evolution, coupled with Bug Type Pokémon's rapid early growth and slow late growth.
Even now, while Pidgeotto has reached Advanced Level from Ordinary Advanced Level, Butterfree took almost the same amount of time to reach Advanced Level, showing its growth rate is gradually slowing down.
But Ralts is different; she is still in her basic form and isn't the type of rapid early growth Pokémon like Caterpie. Reaching Ordinary Intermediate in such a short time is already remarkable.
Even Brock couldn't help but be amazed, as Ralts was the fastest-growing Pokémon he had seen.
Reaching Ordinary Intermediate, Ralts now had initial combat capabilities. Against some not-so-strong opponents, Ash could also deploy Ralts in battles.