Oh boy oh boy. Have I been down this road. I LOVE the FE by the way; much more than the FE2. Indeed I love my FE so much I've just decided to sell my big F3. I like the FE more.
First of all, I'd put all considerations of non-Ai lenses to the back of your mind because they require stop down metering -- which means no aperture priority auto mode for instance. Stop down metering means you use the little button on the front of the camera that actually closes the aperture down to what you have set it for (normally you set it but you're still looking through the viewfinder via a fully open lens, for full light for focussing; the meter compensates and the aperture closes when you release the shutter; AI stands for auto-indexing and that's what it dows. non Ai can't so you have to stop down; when you stop down you'll see the screen go dark). You expose at what the meter says is correct when stopped down; then you open up again and focus. If you REALLY love a particular lens it's worth it but for general walk around use go for Ai. There are non-Ai lenses that have been upgraded to Ai. This is usually explained by the person selling it. If you ever wonder which version you're looking at, use the serial number to check it here:
http://www.photosynthesis.co.nz/nikon/lenses.html
That's the best most reliable source. You can tell an Ai, AiS or upgraded to Ai lens because it has the second row of aperture numbers below the main row. Other sites will explain all this to you in detail. In AIS versions of all lenses the highest aperture number (16, or 22, or 32) are in orange both above and below. In Ai they're different colors.
The 105/2.5 Ai version (not the later AiS which has gotten pricey) can be had for about 100 bucks if you're patient and watchful. Check KEH.com. These two versions are optically identical. Some non-Ai 105s are gauss, some are sonnar. Serials No. 400,xxx and up are gauss.
The 105 is a legend, and rightly so. However I do agree 85mm is better for street work and is also a great portrait lens. It's not transcendent as the 105 often is... but it works.
On the 85/2 --- I too have loyally and often used the Bjorn Rorslett site that you were recommended to above; it's very very good. But he does have some prejudices and this lens is one of them. He does not like it. However, I like it and many others like it. You won't find it for $100 though; more like 175-ish I'd say. Again, always check KEH before buying on eBay because it's a reputable place that takes returns; it uses a very conservative rating system that you can absolutely rely on; and there is no reason to pay more on the auction site than you'd pay KEH.
So. You have a 50/1.4. Here's what I'd say over time you'd like to add:
The Ai or AiS 20mm f/3.5 -- it's usually the cheapest of Nikon's 20mm lenses and is just delightful in my experience. I love mine. There are sharper 20's -- minolta's for instance -- and in general Nikon is better at longer lenses than anyone, but not at wides (excepting the 28mm's mentioned above) -- but this lens is sharp enough, certainly, and has very reasonable distortion and just a great look.
I'm a big fan of 24mm lenses -- of that angle of view -- but I'm not a big fan of Nikon 24mm lenses. I've never had one that I liked, and I've tried 4 of them.
The 28mm: Ah. This is important: DO NOT buy the Ai version of the 28mm f/2.8. It's by every report I've ever seen an inferior product. The 28/2.8 AIS is another one of Nikon's legends. It will run you $200 or so. The 28/3.5 much cheaper. I've not used one but many love it. I have the 28/2.0 which is technically, long distance, supposed to be sharper than the f2.8 but that f/2.8 does have a magical look. And when you use it down at .2 meter (like 7 inches? and that's from the film plane, not the front of the lens, so more lie 2-3 inches) you can get really spectacular shots. The close range correction above referred to is accomplished by a floating element in the lens: it moves as you focus closer. I believe this was one of the first lenses to have it.
I think everyone should have a 35mm. More important than a 28 I think, and even though it seems so close to 50 it's not the same. It's wide and 50's not. Nikon has a very good cheap 35mm: the Series E 35mm f/2.5. It's sharp with good color rendition. I'd get one right away. The 35mm f/2 is priceier and a very good lens. The classic is the 35mm f/1.4 but you won't see one for less than $500.
85/105 as discussed. For the $100 price tag you cannot beat the Ai 105/2.5 and you can make it work on the streets. The 85 is more natural for that kind of work but you'll pay more and ultimately the 105 is the lens you want to own.
I'd skip 135mm.
The Nikon 200mm f/4 Ai or Ais versions are really sharp and really cheap.
Your other option is the Ai 80-200mm f/4.5 or the Ais 80-200mm f/4. These are great MF zooms. Gives you a lot of flexibility. Don't NOT get the 105 though. It's a spiritual necessity. The MF 80-200 zooms will run you about $80-120. Again, check KEH.
As you get richer, or as in my case as you get more addicted to this stuff even though you have no money, here are a couple of other lenses to consider:
The Ais 180mm f/2.8 ED version. Really amazing. This one has spiritual qualities akin to the 105 and the 28/2.8.
The Ais 300mm f/4.5 ED version. The best long lens for the money.
Ideally if you had 20/3.5, a 28/2.8, a 35mm of your choice, your 50mm or the f/2, the 105/2.5, and the 180 ED -- six lenses, five new to you, about $800 if you're careful and patient, you'd walk among the Nikon gods....
Clearly I've enjoyed myself thinking about this. Too much....