I have 2 water bottle cages and a pump on my frame. I have a small seat bag that carries spare tube and tools and a small bike chain lock. In the front I have a small handlebar bag that carries snacks and lunch and sunscreen and route sheet or map and cell phone. I keep a small wallet (with health insurance card) and car keys in my jersey pockets so if they are needed they are on me. Mostly I am riding with a club or friends for several hours.

I don't shop with my bike or do errands on my bike because I live out of town. So, it's quite a different set of things that you need depending on what kind of ride you are doing. Long rides need water and fuel. It's not fun to run out.