India has a rich cultural heritage and mythology. 330000000 gods (Acoording to Hymns) and many many legends. How different would life be in Ancient (not Indus Valley) India if all these legends would be true. As in Gods do grant boons to you if you pray to them devotedly. Mythological Villains exist and have been known to disrupt life. In all gods exist and people do look upon to them. Though they appear only occasionaly and to a few people who are either very nice or very horrible (deserve godly attention). But their existence is unquestioned.
I really don't understand the question. I assume that the vast majority of Hindus in India already live their lives assuming their gods are real. So the humans' lives and rituals wouldn't be so different.
So all you need to do is to create a new set of characters (the gods) and insert them on your books. The characters are already pre-created (you just need to study the mythology) so you already know their personalities and names. And you'll just have to write their actions on your book in a manner consistent to their properties on the mythology (if a god is associated with certain natural phenomena or to answering prayers, make it so).
That sounds like a beautifully competitive market for gods. You're around 1 god for every 3.8 people. Any gods wanting prayers and offerings are actually going to have to do a day's work answering them or they're not getting squat.
What we need to know here is what the gods get out of prayers and offerings and how much they're willing to do in return. There's also a question of how many prayers a god can answer in a day. We could say 80-100 tickets a day which still leaves plenty of time in the evening for cavorting with nymphs.
How often does the average person pray? How often should one actually respond to maintain belief rather than a customer service culture, or is a customer service culture going to be a good thing here? Would that many gods still be treated as gods once they're that active or would it switch to moaning about what they didn't do rather than thanking them for what they did?
Would the gods be better off throwing thunderbolts rather than granting boons? At least that would maintain the respect of the people, spare the thunderbolts and spoil the congregation still holds true.
Once supernatural beings start taking a direct interest in day to day life, the whole shebang would be come so different as to be unrecognisable.