Day 1 - Starts with Pikachu. Steals Misty's Bike. Defeats 1000 Spearow. Misty tags along. Leader Spearow evolved during chase into Fearow. Ash catches the defeated Fearow. Team Rocket attacks Viridian Pokemon Centre - Ash easily wins thanks to Pikachu and Fearow.
Pikachu - Level 35
Fearow - Level 22
Day 2 - Ash enters Viridian Forest. On the way there, a Mankey Steals his hat, and Pikachu shocks it enough for Ash to capture it. Catches Caterpie and Pidgeotto later in the forest.
Pikachu - Level 35
Fearow - Level 24
Mankey - Level 16
Pidgeotto - level 18
Caterpie - Level 8
Day 3 - Caterpie Evolves into Metapod after defeating Team Rocket
Pikachu - Level 35
Fearow - Level 26
Mankey - Level 20
Pidgeotto - level 21
Metapod - Level 12
Day 4 - Ash battles Samurai. Metapod beats Pinsir. Evolves to defeat 50 Beedrill, other mons take on and defeat a few as well. Ash catches Beedrill swarm boss.
Pikachu - Level 36
Fearow - Level 30
Mankey - Level 27
Pidgeotto - level 28
Butterfree - Level 33
Beedrill - Level 24
Day 5 - Ash arrives that afternoon in Pewter City after some training. Meets Flint, hears about gym battles, decides to take part. First though, wants to do some training, gets advice from Flint, powers Pikachu up at Water Mill, and trains the rest of his team a little bit, also finds a Shellder in the river.
Pikachu - Level 37
Fearow - Level 31
Mankey - Level 30
Pidgeotto - level 30
Butterfree - Level 34
Beedrill - Level 25
Shellder - Level 21 > Shellder - Level 22
Day 6 - Ash meets and defeats Brock much easier than his canon self would, using Mankey and Shellder evolved into Cloyster with a water stone. Brock Decides to tag along with Ash after shenanigans.
Pikachu - Level 39
Fearow - Level 32
Mankey - Level 31
Pidgeotto - level 31
Butterfree - Level 34
Beedrill - Level 26
Cloyster - Level 24
Day 7 - Ash reaches Mt Moon alongside Brock and Misty. Catches a Zubat and Geodude, chases off Team Rocket twice to save the Clefairy.
Pikachu - Level 40
Fearow - Level 33
Mankey - Level 32
Pidgeotto - level 32
Butterfree - Level 35
Beedrill - Level 29
Cloyster - Level 26
Geodude - Level 21
Zubat - Level 20
Day 8 - Ash arrives in Cerulean City. Challenges the gym, fights Misty instead. Crushes her with Pidgeotto and Beedrill. Then defeats Team Rocket as well, getting his 2nd badge.
Pikachu - Level 41 (Misty Team)
Fearow - Level 35
Mankey- Level 33 Staryu - Level 25
Pidgeotto - level 33 Starmie - Level 23
Butterfree - Level 37 Goldeen - Level 20
Beedrill - Level 31
Cloyster - Level 28
Geodude - Level 24
Zubat - Level 23
Day 9-11 - Ash deals with Poketech Academy, meets Bill, captures Krabby. Runs off Team Rocket for attacking giant Dragonite. Misty with Cobalt's help catches Poliwag using Starmie
Pikachu - Level 42
Fearow - Level 37 Misty
Mankey - Level 34 Poliwag - level 35
Pidgeotto - level 34 Staryu - Level 27
Butterfree - Level 39 Starmie - Level 26
Beedrill - Level 34 Goldeen - Level 22
Cloyster - Level 31 Brock
Geodude - Level 28 Onix - Level 35
Zubat - Level 27 Geodude - Level 33
Krabby - Level 25 Zubat - Level 26
Ash is a fusion of his anime self, his 20th movie remake self and his manga self. Mostly his alternate self from the Electric Tales of Pikachu Manga. But also the manga version of the anime, which while mostly the same features a much more competent Ash. For instance, in the anime, he loses to Drake of the Hoenn Elite Four easily. But in the manga? He actually wins their battle.
This Ash is incredibly competent.