One common theme is Gino's loyalty. Many fanfics explore how his loyalty to the Britannian Empire or to certain characters affects his decisions. For example, how he balances his loyalty to the empire with his personal beliefs.
Well, aside from the big fanfic platforms, you could also check out some Code Geass - dedicated forums. Sometimes, fans will post their own fanfics directly on these forums. They might not be as well - organized as the big sites, but you can find some real gems. For example, some smaller forums might have fanfics that are more focused on Gino's character development in unique ways that you might not find on the more mainstream platforms.
Yes, it is. As a 'Code Geass' fan, it gives you more content related to the series. You get to explore the story further and might discover new aspects of the characters and the world.
Code Geass did start as a manga. However, its anime version became even more widely known and beloved. The manga provided the foundation for the rich story and characters that were further developed in the anime.
Code Geass started as an anime. The manga was based on the anime's success and came after to expand the story for fans. Some elements might differ between the two, but the anime was the original form.