Flat kit, obviously. Food and water. Probably more than you think you need. I try to eat a calorie-dense breakfast, then I take at least 2 packages of shot blocks with me if I want to do more than around 25 miles. I also keep an emergency gel in my seat bag--I hate the texture, so I'm only going to eat it if it is an emergency! On rides longer than 35 miles or so, I need protein. It's fine if there's somewhere to stop for food, but I'd pack something just in case. Beef jerky, peanut butter, whatever works for you.