What are the best Nikon Pre-AI lenses for Nikon DF?

What was great before (during the film era) are still great now.

There are quite a lot of very good of non-AI lenses.  Opticallimits.com does a great job in showing the optical performance (sharpness, distortion levels, bokeh, etc...).

Not sure why you'd want to use non-AI lenses except maybe for a specific look that some may produce.  Non-AI lenses are pre 1977. 

There's a photographer who's extremely knowledgeable about all things Nikon at https://www.youtube.com/channel/UCVcxJ9k14bi__-uA1...

I would send this guy an email asking about the best non-ai portrait lenses.  From what I know, he answers all of his emails and comments.  I think he'd be an excellent source to ask your question.

Generally speaking, but not always, when a brand like Nikon has multiple lenses of the same focal length, the best ones tend to be those with faster f/stops.  For example the typical 85mm f/1.8 is not quite as good as the 85mm f/1.4.  However, I've seen quite a lot of examples where f/1.2 lenses were not as good as the f/1.4 equivalents.  An 85mm f/1.2 vs an 85mm f/1.4 or a 50mm f/1.2 vs a 50mm f/1.4 are good examples.

The best focal lengths for portraiture are between 85mm and 150mm.  Therefore I'd look for one of these Nikon lenses.  But I think Ken will be able to tell you more definitively which Nikon is best for your needs and within your budget.  Make sure to include your budget when you send him an email.  Makes no sense to recommend a lens you can't afford, right?

Pre-AI is not any different than non-AI. Both terms are used for lenses that do not have the AI notch. Non-AI lenses were not recommended for use with Nikon cameras with the AI metering system because they can actually damage the AI system physically. There is no advantage using these lenses. Metering is also inconvenient. Besides, the older lenses were generally not as well designed since super computers and exotic glass and aspherical elements were extremely rare back then. You are better off with AI lenses and even AF lenses. The earliest Nikon zoom lenses, such as the  43~86mm, for example were garbage compared to modern lenses. Perhaps the best non-Ai lenses made is the Vivitar Series 1 90mm f/2.5 macro lens, but it is actually the same lens as the Tokina AT-X 90mm f/2.5 lens optically. Other Series 1 lenses made at the same time, such as 28mm f/1.9, the 135mm f/2.3 and the 200mm f/3 may be worth getting if they are reasonably priced.