Pokemon Pokemon Let’s Go Pikachu and Pokemon Let’s Go Eevee are games that take place in the Kanto region with similarities to Pokemon Red, Blue, Green, and Yellow, as well as Pokemon Firered and Leafgreen. The games give you the limitation of only being able to use Pokemon originally introduced in Generation 1, with the only exceptions being Alola forms and Meltan. Pre-evolutions and evolutions of Generation 1 Pokemon not introduced in Generation 1 are not available. However, Generation 1 introduced the second highest number of Pokemon. They have a wide array of type combinations, with every type being included at least once (if you include Alola forms. If you exclude those Dark is the only type not represented). However, for the sake of argument, I’m going to include any Pokemon that can be obtained in the game.
I’m going to split this up into two scenarios: one for Pikachu and one for Eevee. Pikachu, being an Electric type, means it would be useful for Water and Flying types. Although there is a Water type leader, there is no Flying type leader. However, there are leaders who use Flying types. However, Electric types are resisted by Grass, Electric, and Dragon types, and all of these types are represented in gym leaders, so we’ll need types to cover those weakness.
For Pikachu, your second Pokemon should be Oddish. Oddish is a Pokemon that can be found at a maximum level of 8 on Route 2 just before Pewter City. It will also be useful for Brock, Giovanni, and Misty. For your third Pokemon, get a Geodude. They can be found at Mt. Moon, at a maximum level of 10. It will be handy for Lt. Surge and Blaine. For your fourth Pokemon, get a Drowzee. They can be found at a maximum level of 18 on Route 11. It will be helpful for Koga and Bruno. For your fifth Pokemon, get an Alolan Sandshrew. They can be traded for regular Sandshrew in the Celadon City Pokemon Center. It will be practical for Erika and Lance. For your sixth Pokemon, get an Alolan Rattata. They can be traded for regular Rattata in the Cerulean City Pokemon Center. It will be convenient for Sabrina and Agatha. Switch out Pikachu for Hitmonchan. It will serviceable for Lorelei.
For Eevee, do the same thing except have Bellsprout instead of Oddish and Alolan Vulpix instead of Alolan Sandshrew.