Rival Choice Event

In mine will have 2 options of players to choose ash and gary, when choose ashes automatically my irval will be gary and if gary choose my rival will be gray. How do I do that?

1. Add a condition that if the player selects Gary, a switch gets turned on.
2. Whenever you want to have a rival encounter, make an event containing a placeholder NPC.
3. Make a new event page that contains a graphic of Gary and all of Gary's events. Make sure the page only activates if the aforementioned switch is turned on.

Don't forget to do the same for Ash.

I'm not good at this, can you help me?

He just posted step by step instructions. Maybe try those and see if they work. If not, then post pictures of what you've tried. It's easier to help you that way, and you learn how to do it yourself better too.