Updated OP
Is it already outdate or did I miss anyone?
Also, what levels are his mons at, so I know how much I should train.
Whose, Cheren's? He was level 12-14 for me I believe although I'm on Challenge Mode. Idk if that means higher levels for gym leaders or an extra Pokemon or both.
I'm worried what I'll do about Roxie - Oshawott would be normally effective and Riolu will be not very effective. I might just train up Mareep a bit more for now. I know she has a Venipede or Whirlipede though so maybe I should train Pidove for a bit instead though...
On normal mode, his Pokemon are level 11 and 13 respectively. Level 14 usually works for me, but just to be safe, you might want to train up to level 15 or 16. Cheren is a pain to fight.