Which Seven Knights selector should I pick?

For early game progression, I recommend leveling up your fodder farming DPS first. After that, you can focus on leveling up your arena heroes or raid heroes. For fodder farming DPS, I recommend heroes like Taeo, Freya, Omok, and Klahan. I personally leveled my fodder farming DPS to 6-star first, then focused on leveling up my arena heroes.

I picked Rachel and Rudy from the selector. I'm using Teo for leveling fodder and as a main DPS since they just gave him away. I picked Rachel because they said a raid hero was needed for weapon farming, and while not for every dungeon... anyway, I was trying to complete the mission to reach Gold tier in the Arena and kept getting stomped by Delons, so I picked him too.

When and where was the choice given? Why don't I remember making one?