The most practical all-purpose lens you could put on it would be a 50/1.8 Canon (early ones are marked Serenar). Far easier to find one in fine shape, because it has hard coating, and is a rigid lens. It is also a very fine lens, known by many as a "Summicron killer". It probably really is better in many ways than the Summicrons of the 1950's. It's not a lens with a lot of "character", it's just a darned good lens.
You have to be a more careful shopper to buy a Leitz lens for it. That's because all the 50mm collapsible screwmounts have very soft front glass, soft coatings, or both.
Summitar 50/2 is a great lens for B&W, fine for color, too. Comes in coated and uncoated -- but often front glass is scratched to hell.
Summicron 50/2 is a potentially better lens than the Summitar, but boy is it prone to internal haze, and it's often the case that the haze causes permanent damage. Also, the front glass is often a mess.
For these Leitz lenses, you either have to be lucky, or be a smart shopper in-person. Or deal with a very reputable dealer. I did OK on eBay for my Summar (even earlier lens) and Summitar, but my Summicron is not great.