Darumaka/ Darmanitan (Desert Resort) or Growlithe/ Arcanine (Virbank Complex/Route 7) are essential for upcoming challenges.
I can give you specific team-building or strategy advice based on where you are. Pokémon League - Pokémon Black 2 and White 2 Guide black2-8
are you currently working towards (e.g., 5th, 6th, or 7th)? What is your current team ? black2-8