Grepolis has eight gods: Zeus, Poseidon, Athena, Hera, Hades, Artemis, Aphrodite and Ares. Each offers divine powers and two associated mythical units. A city worships one god at a time, so choose according to what that polis needs.
Plan around the city role
Consider whether the city supports economy, naval action, land attack or defence. Compare the current powers and unit costs in the Temple rather than relying on a universal “best god” list.
Think before switching
Changing gods can remove accumulated favour and units associated with the previous god. Time a switch carefully, especially if a spell or army is already in motion.
Read the mythical units guide, defence guide and complete Grepolis guide.