My advice is start with a 150mm, as it is extremely versatile but still easy to work with, focus and has tons of image circle for movements (even cheap ones). I bought a 210 to start and quickly then bought a 150 and a 90. Only been doing 4x5 two months, but I never use the 210 at this point. It's a weird focal length (longer than normal but not long enough to feel like 85mm on 135 film or 150 on 120 film) and I don't really understand why there is all this advice out there to start that way. You can always crop a photo taken with a 150 to look more like 210, but you can't do the reverse.