Question – what would the gods give in return for sacrifices?
It would have to depend on what you sacrificed. An imp – mebbe a couple of Gold coins.
Something valuable – like a bunch of mana or a level 10 Legendary Humanoid, or a high level item should net you a permanent extra power. Each god could offer a summon or artefact or something. E.g. the God of darkness could give you the power to summon shadows.
The gods in a pantheistic setting are in competition, so I reckon they would be fairly reliable in ponying up goodies to a loyal worshipper.