There's an old joke that goes something like "Tell me everything you know...while standing on one leg". Your question is like that. The amount of stuff to know about Lugers is enormous.
To keep it simple: If you want a good shooting Luger, the thing to look for, IMO, is an East German rework Luger. These are Lugers reconditioned by the East Germans and given a heavy black refinish. They are sometimes called "VOPO" Lugers, for VolksPolizei, or the Peoples Police, but I think most of them really just went into storage until East Germany collapsed and they were exported to the US.
Luger collectors are, or were, not very interested in them because of the refinishing, and most people say they work pretty well. I don't know how available they are now.
That's all the useful advice I have to give. I've been collecting guns since the early 1980's, and I've never acquired the specialized knowledge about Lugers needed to tell a good one from a bad one. That's why I bought an East German one - same as you, I just wanted a good shooter. I was lucky that world history made that convenient for me.
PS - if you want a good shooter, stay away from the Mitchell or Stoeger Lugers. They were made for a while in the 1980's out of stainless steel. They're an interesting part of Luger history, but the one I had jammed a lot and shot high and to the right. Also, after the first year, Mitchell gave up on trying to make their magazines hold 8 rounds, and de-rated them to 7.