I'm a nromally big chested gal. I remember being told to stay away from underwire bras as they can cause the ducts to clog.
At night or when I was home, I wore those bed-time nursing bras. I'm not sure what they are called, but they were just like t-shirt material that I was able to insert the pads into and made it easy to quickly whip out a boob to nurse at 2am. During the day I usually wore a t-shirt or something over it, but at night, that's all I slept in (well and a pair of pajama pants or something else lol.)
During the day adn when i returned to work, I just wore clothing that I could maneuver to get the pump into. I didn't buy any specific nursing clothing aside from a few nursing bras, but then again, I am someone who dresses for comfort most of the time.
Dont spend a lot now. wait until you are sure what you want and then go shopping.