The bayonet mount "M" series are probably your best bet for your first Leica. The earlier models make you use the rangefinder window first to focus then you need to switch to the viewfinder window to frame your subject. That's kind of a problem if you've never used one before. Also, the III series is a screw mount. If you get any lenses other than a 50 mm you will have to get an viewfinder that fits in the hot shoe.
The m series allows you to focus and view in the same viewfinder window. Also, the m2 has framing brackets for 35, 50, 90mm lenses, while the m3 has framing brackets for 50, 90 and 135mm lenses. The m3 body will have either a double stroke or single stroke film advance, depending on the date of manufacture. No sure if the m2 is a double stroke or not.
If you have the money, the m4 is a great camera. It has framing brackets for 35, 50, 90 and 135mm and also has an in-camera meter.
Actually, Leica bodies are not all that expensive, but the lenses are. Reason is that you can use the bayonet lenses on any Leica m series made, including the m9. Screw-mount lenses can be very reasonable and Leica made a mount adaptor that will allow the use of the older lenses on newer bodies.
I just happened to pick up a very nice IIIf on
ebay. Price was 499 with a Summitar collapsible 50mm. The camera is in perfect shape. There were many, many Leicas bought by professionals (doctors, lawyers, etc) simply because of the name and they were hardly used. That means there are some incredibly beautiful Leicas available.