But intuitively eating unprocessed foods that are not made with artificial or chemical anything (including artificial sweeteners) is probably a good start.
Fasting is probably another good way to reset your gut.
I don't think "resetting your gut" is a good way to think about it. Taking oral antibiotics will "reset your gut", in the sense of killing most of the existing biome and leaving space for new flora to grow into, but that can lead to problems as the biome that develops from a clean field isn't the same as the standard biome. To the best of my knowledge, you normally inherit your gut flora from your mother during birth and nursing, and then your gut hopefully stays stable over time. "Resetting" is more likely to give you a worse biome than a better one.
But intuitively eating unprocessed foods that are not made with artificial or chemical anything (including artificial sweeteners) is probably a good start.
Fasting is probably another good way to reset your gut.