Perfect adapter and lens

You've already gotten lots of good advice. I would just add that, in a world with heaps of cheap 50mm manual-focus primes available, you might want to avoid Canon FD lenses. The FD breech mount requires an adapter with a rotating ring to engage the lens aperture pin. Mounting and dismounting the lens to/from the adapter requires a bit of fiddling, which is not necessary for other common lensmounts. It isn't a huge chore, but if you don't already have FD lenses on hand, and since just about any FD focal length/aperture combo is available in many other lensmounts, there isn't much need to cause yourself any extra hassle.