I am no mechanic, so I carry enough to fix a flat: 2 levers, 2 tubes in a ziplock with some powder, a CO2 injector and at least 2 CO2 cartridges. I used to have the Topeak frame pump, but my bikes are really small and if I want 2 bottle cages, I can't do that now. However, I started using Gatorskins (Kevlar tires) almost 4 years ago, and have not had a flat since. I carry tube of Nuun,
an electrolyte tab you put in a water bottle and one spare Lara Bar. My rear bag isn't huge, but not teeny, either. Because I lead rides, I have a ziplock with bandaids, tissue, a few antihistamines, and antibiotic creme. I can stuff arm warmers or an extra head cover, etc in there, too.
I use my jersey or jacket pockets for my wallet, phone, and inhaler. Sometimes for small clothing items, like different gloves, too.
I run blinkie rear and front lights day and night. I use rechargeable lights that are very bright. I have 2 different front lights and one is about as strong as a car light, as I often ride very early in the AM. Both have several settings, as well a a blinking mode. And like NY, I always wear a Road ID, when I am doing any sport.