What's a good recipe you cook that doesn't need expensive ingredients?

Bengali daal - a thin lentil soup, served over rice. Rice and dried lentils are one of the cheapest things you can buy in my country (& probably worldwide) - and this recipe uses very limited ingredients. The spices it uses - Indian bay leaf and kalo jeera - are not expensive in Bengal, and pretty basic/versatile, used in all sorts of dishes. But they're also optional - only daal, salt, water and green chillies are mandatory for making a decent daal!