What season of spartacus god of arena and blood sand which the first season?

I finished the Spartacus DVD, god of the arena, blood and sand, vengeance. And I know vengeance comes after blood and sand, but I wonder which one is the first, god of the arena or blood and sand. What’s the relationship with these two shows?

A4: They are both Sparacus seasons. Blood and Sand was about Spartacus, but the guy who played Spartacus became ill, and had to leave the show. Gods of the Arena is the 2nd season, but is a prequal. It's about Gannicus, who was in the first season, but BEFORE Spartacus was in the picture.