Contrast what Gale and Peeta signify for Katniss. How do each help her succeed in the games?
While she is in the Games, Katniss relies on Gale and Peeta to help her survive in different ways. While Gale represents Katniss' practical knowledge and skills, Peeta represents her more emotional, personal struggle within the Games.
Before becoming a tribute, Katniss and Gale would go hunting outside of their district. During that time, Katniss perfected her skills with her bow and arrows, and she also learned how to make traps from Gale. Because of this experience, she knew she would be able to find food in the Games, and she was more confident in her abilities to defend herself from the other tributes.
Katniss did not have much interaction with Peeta before the Games (aside from when he gave her some bread), but once they were in the Capitol together, things changed. At first, she did resist teaming up with him because her only goal was to survive and get back to her sister, which she knew would be more difficult if she thought of Peeta as a friend. But once the Game-maker announced that two tributes could be victors together if they were from the same district, Katniss' attitude changed: Peeta brought out a more human side of her as she had to take care of him after he was injured trying to help her.
Although it was only Peeta in the Games with Katniss, both he and Gale helped her survive. Gale represented Katniss' past and her own abilities; Peeta represented Katniss' future and what they could do together.