Buy the dress, the second lens will come faster that way! When I got my Mamiya 645 I spent a couple of years with only the 80mm lens, I got so good at it I could look at what I wanted to photograph and when I sat up the camera it was right in the view finder.
I have a 90mm and a 180mm and 2x for my RB67, I find that the 180mm is great for landscapes. Have fun.