You should believe in all of them. Just spray and pray!

You have to filter out all the religions where you can't worship other gods or be in other religions.

Might as well skip the one that don't punish you for not believing as well.

Ah, so all of them. Oh well!

Any God, as long as it's not a being/creature. Thankfully there's only one of those! https://en.wikipedia.org/wiki/Classical_theism