43level cap
Koga (as your 5th badge) fields 4 Pokémon between level 41 and level 43 in Fuchsia City Gym.
This is around Beat Koga — Fuchsia City Gym, badge 5 in the story — that page lists everything you can have caught by this point.
Types on this team: Poison ×4BugFlyingWater
| Pokémon | Ability & item | Moves | Base stats | |
|---|---|---|---|---|
 | Golbat Lv 42 PoisonFlying | Confuse Ray Toxic Bite Sludge | HP75Attack80Defense70Sp. Atk75Sp. Def75Speed100Total475 | |
 | Muk Lv 42 Poison | Acid Armor Sludge Mega Drain Toxic | HP105Attack105Defense75Sp. Atk85Sp. Def85Speed50Total505 | |
 | Tentacruel Lv 41 WaterPoison | Surf Ice Beam Barrier Sludge | HP80Attack70Defense65Sp. Atk120Sp. Def120Speed100Total555 | |
 | Venomoth Lv 43 BugPoison | Solarbeam Double Team Toxic Psychic | HP70Attack75Defense60Sp. Atk95Sp. Def95Speed100Total495 |
How to beat this team
Shared weaknesses. Psychic hits 4 of 4, Electric hits 2 of 4, Ground hits 2 of 4, Rock hits 2 of 4.
Level to be ready for. Lv 43 — Venomoth, the highest on the team.
Psychic Pokémon you can have caught by this point. From this guide’s own encounter tables, by Beat Koga — Fuchsia City Gym, badge 5: