The entire paragraph is written in a dialect I'm not familiar with, but I expect it is a typical lower-class dialect from around the time and place of the novel (Kent and London in the early to mid-19th century).
I confess I never read "Great Expectations" (although I probably should), but from a glance at the plot summary it seems Pip is just coming back from a visit to a wealthy woman's house where he was made to feel ashamed of his working-class family. To which Joe considers:
As to who you visit socially or work for ... might it be better to continue to keep company with common people (those of your own station) than "uncommon" (upper-class) people?
"Keep company (with)" is a common English expression meaning to associate with, or visit. Also common is the structure "continue to (do something), for example:
He said that, in the long run, it was better if I continue to work on my college degree, rather than drop out to get a job.
Another example from the same chapter of the book:
"Well, Pip," said Joe, "be it so or be it son't, you must be a common scholar afore you can be a oncommon one, I should hope!"
I don't know of any modern dialect that uses "son't", but hopefully you can get the meaning ("be it not so") from context. Similarly "afore" means "before", and although no one I know uses it I think there are many places where it's natural.
Meanwhile, I believe "oncommon" is just a spelling quirk to indicate dialect, although I'm not sure why it's not written "an oncommon". Again, possibly a quirk of that dialect. People still frequently say "I should hope!" though.
You should also imagine both Pip and Joe speaking in a heavy working-class English accent. See this scene from the 1946 movie for the general idea.