Ahh... bag shopping rookie! I started with, and still have (and use daily, and love) my LowePro AW202 Sling Bag. Granted, I only have 3 lenses, flash, diffuser, spare battery, blower, lens pens, AA charger, remote cable, wireless remote, RF triggers, microfiber cloths, and 3 spare SD cards in it, so eventually I'll need to go bigger.
Of course, I have the
tiny little D7100... but I think I found my "Nirvana" a little earlier than most.
It's an easy one shoulder bag with quick access to the camera, @
traceyjj, and worth a look. The have the 302 as a step up (little larger) as well.