How do you keep it organized? Do you use pouches or smaller bags?

I wanted a backpack diaper bag for my second (whose coming soon!). I was eyeing a couple but then I was gifted a really stylish and expensive backpack that I think I can just use. I hate rummaging for things and that's the only drawback. So tips please?

(FYI ... For my toddler, I don't really carry anything for her. Maybe a pack of raisins )