1) It depends individually. There are many mommies who dont't use nursing bras. I personally find nursing bras really useful & convenient when baby was younger. Just need to unhook the flap in front and feed. Now that he's bigger and understands what is "stand and wait", I can go back to my normal bras. I bought 1 cup size bigger.
2) Try Momsinmind. They sometimes have clearance sales and marked down bras. If not, just get 1 first and you can always buy again when you finish confinement.
3) I bought mine early but you can always wait till you deliver to get 1. I prefer electric cos manual is really tiring after a while. Why not look for a 2nd hand set? You only need to replace the funnels, bottles, etc. Definitely cheaper than getting a brand new set.