s+
These characters are essentially always great picks but aren't without their counters, for example, not being able to leave an Odin cage, or having an escape that a strong Awilix player can abuse. Due to the nature of these characters, I would be looking to ban characters from this tier or pick them with your first pick or two.
s
These are really strong characters, any god here can be just as good as gods in S+ depending on the situation; after all, many games are won in the picks & bans. You can pick these gods at any point, they are just simply are a little weaker than the gods above. For example, you can't really pick Sobek if the enemy has Terra and can't be plucked.
s-
Gods in S- are still some of the mode's best characters. But many are counter picks or only work with certain team compositions.
a+
These gods are really solid and you can get away with them in good compositions if you are a competent player. Some characters from this tier might also be strong counters into the correct team composition.
a
These gods aren't the ones you should be looking to select, but they are strong enough counters in certain positions, to the point where they are still good.
a-
None of these characters are ideal, but they still have up-sides such as being able to force the enemy to buy or burn certain relics on cooldown. If you're a top player getting the usually matches against low MMR players you should be able to win consistently on these gods.
b
These gods don't have much going for them; however, they are clearly better than the gods in C and D. You can still win on any of these characters if you're just way better than the opponents.
c
These gods are irrelevant. They don't contribute enough, have way too many counters, or fall off horrendously late game. I wouldn't pick any of them.
d
These characters contribute nothing to your team comp; picking anyone in here is essentially trolling.