Canon FD system, for sure. Good glass, good bodies... Get an AE-1P or an A-1. I think the A-1 has more options for automatic exposure, but if you're going manual shutter and manual aperture they are mostly the same. The AE-1P has a slightly better "feel" to the shutter dial so you can bracket or adjust on the flight with a mini-flick of the finger,
All you really need is the body and a 50mm. I would suggest a 28mm or wide of some sort. Then also perhaps a zoom or telephoto depending on your tastes. The good news is you can probably get the camera in perfect condition, and 3 lenses plus more kit all under $400 (your budget).
Compared to larger formats, 35mm is relatively cheap.
EDIT: P.S. I find myself using my 35-70mm f/2.8 zoom more often lately. It's nice for framing shots better. I would recommend something like this unless you have a dislike for zooms in general.