You don't need a closetful of olive oils, despite the wealth of options, grades, and flavors. One reasonably priced bottle for sauteing and baking and one more-expensive, full-flavored oil for drizzling will serve you well. But if you want just one that switch-hits, go to Costco for Kirkland Signature Estate Extra Virgin ($9 for one liter). Among supermarket brands, Colavita Extra Virgin Olive Oil ($24 for a three-liter tin, www.gourmetstore.net) and Filippo Berio Extra Virgin Olive Oil ($4 for 8.5 ounces) are also good one-oil-fits-all choices.