Since Daniel and Matthew will be going separate ways from Ash and Misty after Mt. Moon or more likely once they get to Cerulean City might be after Pewter City when Ash rechallenges Brock.

Anyway, the point of this is to introduce the main travel group with Daniel and Matthew.

Daniel

Matthew

Amber

Jessie

Meowth (Who joins because he loves Daniel's Meowth)