My newly acquired Sony A7II has the best support I’ve encountered for shooting with legacy lenses. It has a lens mount that supports a huge range of adapters, a great electronic viewfinder, good camera customization options and most importantly excellent focusing aids. These cameras have the right mix of tools for using non-system lenses.
Once you have the right camera you have to decide which legacy lenses to use. Actually this has been difficult for me. I started out with the idea of using some Olympus OM glass I already owned. I will have to expand my reach to other lens makers in order to get the best possible image quality for the least cost. The problem is objective information about legacy lens quality is surprisingly hard to find.
If you want good to excellent glass at a good price you have to do some homework. High end legacy glass users only recommend high end lenses and gearheads will use anything at all. To help find the right glass at the right price I expanded my reach by purchasing an M42 lens adapter. Using the M42 mount gives me the option of trying out literally hundreds of different lenses from more than a dozen makers. To put one toe in the water I bought a cheap Super Takumar 35mm 3.5 lens on EBay the other day. I suspect this will be the first of many M42 lenses I’ll try over the next year.