Now, except for the Unitas 6498, which can be found in many inexpensive Nastrix pocket watches on eBay, I've been using Russian movements to learn watch servicing and repairing. To the best of my knowledge and experience, these Russian movements are some of the most affordable on the market. In some cases, like with the Poljot 2614.2h, the Russians have copied Swiss movements and have adjusted them to be more rugged. There's a really cool article about it here.
An interesting aspect of these movements is that they have their roots in the era of the Soviet Union, meaning that the movements were not the result of a free market, but ordered by the Russian state to provide the masses with a way to tell time. As a result, these movements were designed so that they could be serviced using just tweezers, a couple of screwdrivers, and a bit of watch oil. Ideal for any beginning watch repairer.
As an indication of their affordability, a brand new 32 Jewel Automatic Vostok calibre 2416B is about $40 (and if you buy 10 or more $33). On eBay, you can find fully working Russian watches, that more than likely need service, for less than $20 with free shipping.
My favourite brand is Vostok (sometimes spelt Wostok, Boctok, or восток) especially the Komandirskie and Amphibian models. It was this video that got me into Amphibians. Vostok, Poljot, and Raketa are the big Russian brands.
Needless to say, I'm very fond of Russian watches and movements, and although the appreciation for them isn't that great on WRT (yet), there is a pretty large community found on the F10 forum on watchuseek.com. These watches are also very easy to customize and many do.