The word you're looking for is autodidact, not polymath. And unfortunately, it's not really possible to have the learning experience of a law student without the guidance of professors. You can teach yourself legal doctrine from textbooks, but I'm not sure how interesting that will be when you'll have little sense about how to apply it.
Here's an example of a popular textbook used in 1L Property Law: https://www.amazon.com/Property-Connected-Casebook-Aspen/dp/1454881992