A little over a year ago, I took a political philosophy course, and am currently reviewing some notes and the texts. Keeping in mind that I have no other background in philosophy, I wondered if anyone could recommend a good place to pick up from and keep learning about the subject. I'm certainly willing to venture into other areas of philosophy as well.
For reference, through the class I read Plato's Republic, most of Aristotle's Politics, Machiavelli's The Prince, Hobbes' Leviathan, and selected essays by Kant and Marx. Through Kant, I felt like I was reasonably able to keep up, but with Marx, although my professor assured me I understood the basics well enough for the class, felt like quite a stretch to understand, like we had skipped important background info (and I remember Hegel being mentioned in his writing frequently). I'm certain Plato's political ideas aren't solely contained in that text, and wondered if I should start by going back and reading other of his or Aristotle's works, then moving forward, or if not, then what a good next step would be given that I have familiarity with these particular writings.
I think that, basically, what I'm asking is this: are there major gaps I need to fill to even make sure I have a grasp of these, or can I move on? And if I am to move on, who or what could I read and understand given this background, that would also help me build a larger base to keep studying from there?