There's a great article at The New York Times by Mark Bittman about must-haves in the kitchen. I've read a few articles by him (notably one about how tiny his kitchen is) and I like his style. He keeps things simple (thus, "The Minimalist") and is no-nonsense in his cooking approach.
I think the best place to start is to start saving your jars and then start a collection of grains and dried beans, and then experiment with those. Also, keeping lemons in the house is great, not only for cooking, but for adding to water. I like to start my day, many days, with a big glass of water with a whole lemon squeezed into it. On those days, I am more awake than usual. It's also great for your liver, I understand.