Eastern lowland gorillas have more diverse diets, which vary seasonally. Leaves and pith are commonly eaten, but fruits can make up as much as 25% of their diets. https://en.wikipedia.org/wiki/Gorilla#Food_and_foraging
The mountain gorilla is primarily a herbivore; the majority of its diet is composed of the leaves, shoots and stems (85.8%) of 142 plant species. It also feeds on bark (6.9%), roots (3.3%), flowers (2.3%), and fruit (1.7%) https://en.wikipedia.org/wiki/Mountain_gorilla#Habitat_and_ecology