What to buy?!

I'm a FTM and it's just starting to hit me that this is REAL. I'm only 15 weeks but trying to make some kind of plan. Here's where you come in, hopefully! When did you first start purchasing baby stuff? What were your favorite baby stores? What are things you realized you could and couldn't live without? I'm trying not to jump the gun and start buying, but planning out what to get and where to go is so helpful for me mentally. Any and all tips are welcome. Please, share!!