Alex, congratulations on the F6. I also buy only new because I was disappointed that the 80 - 200mm f2.8 AF-S lens that I loved after buying it used could not be repaired. I decided on a new 70 - 200mm lens rather than another used 80 - 200mm. I want it to be reliable and repairable as long as possible.
The Nikkor AF-S 1.8/50 is almost a legendary lens along with being small and inexpensive. However, I think you should decide what your final set of lenses would be and buy one of the lenses on that list. It depends on what focal lengths and apertures you actually use. I would never use a 50mm lens. But an 85mm f1.4 will always be in my set.