Some of my best buys are :
Sam's club: Frozen fruit, walnuts, and almonds are by far cheaper in bulk there.
Winco: Quinoa, agave nectar, and hummus are cheapest there. Their bulk food
section is amazing. If you don't have a Winco, I've heard Whole
Foods is good for these things as well.
Local health food Store or Amazon.com: I get my coconut oil, sea salt, sucanat, and brazil