More context would be helpful, but going by what you have provided here, this reads like a piece of general advice given to an unspecified audience, in which case, yes, if you add a generic you, it'd make sense. The author is talking to the reader in such a way that they expect the reader to want to learn from them. You could say the tone is patronizing. And you are right this sentence does contain cascaded relative clauses. For more on relative clauses in Japanese, check out this answer.
ことfunctions as a nominalizer that marks a thing that is suggested to the reader/listener. See entry 10 on jisho.org. So your original sentence means
If you find a place with a lot of like-minded people, go there without cease.