50level cap
Koga (as your 6th badge) fields 5 Pokémon between level 48 and level 50 in Fuchsia City Gym.
This is around Beat Sabrina — Saffron City Gym, badge 6 in the story — that page lists everything you can have caught by this point.
Types on this team: Poison ×5BugFlyingWater
| Pokémon | Ability & item | Moves | Base stats | |
|---|---|---|---|---|
 | Golbat Lv 49 PoisonFlying | Toxic Confuse Ray Sludge Bite | HP75Attack80Defense70Sp. Atk75Sp. Def75Speed100Total475 | |
 | Muk Lv 48 Poison | Sludge Mega Drain Toxic Acid Armor | HP105Attack105Defense75Sp. Atk85Sp. Def85Speed50Total505 | |
 | Tentacruel Lv 49 WaterPoison | Barrier Surf Ice Beam Wrap | HP80Attack70Defense65Sp. Atk120Sp. Def120Speed100Total555 | |
 | Weezing Lv 48 Poison | Amnesia Sludge Thunderbolt Explosion | HP65Attack90Defense120Sp. Atk85Sp. Def85Speed60Total505 | |
 | Venomoth Lv 50 BugPoison | Solarbeam Double Team Toxic Sludge | HP70Attack75Defense60Sp. Atk95Sp. Def95Speed100Total495 |
How to beat this team
Shared weaknesses. Psychic hits 5 of 5, Ground hits 3 of 5, Electric hits 2 of 5, Rock hits 2 of 5.
Level to be ready for. Lv 50 — Venomoth, the highest on the team.
Psychic Pokémon you can have caught by this point. From this guide’s own encounter tables, by Beat Sabrina — Saffron City Gym, badge 6: