Hi,
I have been a dedicated OM user for over 25 years. My advice to you if you are interested in Olympus is to start simply and see how you get along with the camera. The OM system is a very extensive and capable system and I have been adding lenses and other bits and pieces aggressively for several years now and there are still a lot of things that I don't have yet.

1) The 28mm f2.0 Zuiko---

The 28mm f2.0 Zuiko, the 90mm f2.0 Zuiko-Macro and the 180mm f2.0 Zuiko are the only three f2.0 OM lenses that I do NOT own. I have the 21mm f2.0, and the 24mm f2.0 which take 55mm filters. The 28mm f2.0 Zuiko takes a 49mm filter and the lens hoods are much more readily available. The 28mm F2.0 lens had one revision from the original. The later version had 9 elements in 8 groups. Like the other F2.0 wide angle Zuikos, the 28mm uses a floating element design to correct for close focusing distances. Earlier lenses with the "MC" designation on the front are Multi-Coated. I never heard anything bad about the 28mm F2.

Here is an example from the 21mm F2.0 Zuiko:Tracks.jpg

2) The 50mm f1.4 Zuiko and 50mm f1.8 Zuiko---

I have a fair amount of experience with the OM standard focal length lenses. My first 50mm lens was a 50mm F1.4 Zuiko with serial #1,123,989 and I bought it new in about 1985. It is my most used lens. I like it well enough that I bought another a few years ago so that I will always have a back-up. This lens is quite sharp even at wide apertures and I would not be without one. I also have a silver nose 50mm f1.4 G. Zuiko and it is also a good performer but not quite as good as the later ones. The Olympus nomenclature of G. Zuiko means that the lens is single coated. Having the f1.4 aperture is quite valuable indoor or in low light, especially if you don't like to use flash. Definitely get a hood. They are easy to find and relatively cheap.

I also have a 50mm f1.8 Zuiko and the reputation of these is that they are incredibly sharp. My copy certainly is.

I also have the 40mm F2.0 and the 50mm F2.0 Macro lenses. The 40mm I use sparingly and the 50mm f2.0 Zuiko-Macro I am using quite a lot. Here is a sample from the 50mm f2:August_Grass.jpg

3) The 35mm F2.0 Zuiko vs. the 40mm F2.0 Zuiko---

I have both of these but these are seldom used. They are too close to 50mm which is my most used focal length. Of the two I prefer the 35mm f2.0 which I find to be more useful.

4) The 85mm f2.0 Zuiko---

Of the four Zuikos from 85mm to 100mm the two with the best reputation are the 90mm f2.0 Zuiko-Macro and the 100mm Zuiko f2.0. I own the 100mm f2.0. This lens is a real beauty. Extra-low dispersion glass, and close focus correction for aberation. Seven elements in six groups. This lens is amazingly sharp and a great performer even at f 2.0. The only one that is better in the Olympus line-up is the 90mm f 2.0 Zuiko-Macro. I also have the 85mm f2.0 and it is a good lens and give you more bang-for-the-buck.

5) Serial number/Labeling---

Most of the lenses were improved over time. Some people have complained that build quality was better with earlier lenses. Earlier lenses labeled MC are multi-coated. Lenses labeled F. Zuiko, G. Zuiko, or H. Zuiko are single coated. All lenses made after about 1982 or so are multi-coated. Most of the lens line saw changes over the 30 years of production. It depends what focal lengths you are looking at.

6) Winders and Motor Drives---

Winder 1 and Winder 2 give a rate of 2.5 frames per second and Motor Drive 1 and Motor Drive 2 give you 5 frames per second. Winders use AA batteries and the Motor Drives use the dedicated Ni-Cad Control Packs or the M. 18v Control Grip. I use mostly OM-4T's with Motor Drive 2 and the M. 15V Ni-Cad Control Pack 2. Chances are about 90% that the Ni-Cad cell are kaput which means that you will pay $150 to get the pack re-celled and overhauled. The Winders are probably a better choice for most casual users.