Assuming 5x4: Looking at the range of subjects (portraits, landscape, architecture, products), you would probably do well with a 210mm. That's at the long end of 'standard'. It would give you some working distance for table-top work, and be a reasonable lens for portraits. Not good for cramped interiors though. Then you would probably look at a 90mm or maybe a 75mm. On the other hand, my Wista has a 90, 150, and 270 setup and I mostly do landscapes.
Try and get your hands on a copy of Steve Simmons' 'Using the View Camera', or Jim Stone's 'A Users Guide to the View Camera'. That will not only walk you through the technicalities of lenses, but show some practical examples.