I would make a division between (1) all the things you need to know to do philosophy and (2) important books and (3) "State of art"-philosophy if one wants to call it like that (those papers, essays and books that are written in the last 20 years or so, by people who we pay to do philosophy).
(1) In order to get into philosophical terms etc. I would suggest the book: "Philosophical Devices: Proofs, Probabilities, Possibilities and Sets", by David Papineau. I read it and it is awesome and very helpful. Another one that comes up often is Thomas Nagels "What Does It All Mean?: A Very Short Introduction to Philosophy".
You would then know the relevant terms and got a neat overview what schools there are etc.
(2) Next step would be to read whatever you like. Let us pretend you are mostly interested in political philosophy. Then i´d go chronological and start by Platos Republic, Hobbes Leviathan, Rousseaus Social Contract, Kants Perpetual Peace, maybe mix some Marx in, and finally Rawls Theory of Justice. Depending wether you like Rawls or not, you can go into any direction from there (Nozick would be one example). Of course there might be different views on which books one should read. These books are probably found on the reading list of introductory courses for political philosophy at a lot of universities, though.
(3) If you´re done there, I would suggest, whatever your interest is after reading all this, to read what is written nowadays or in the past 20 years, e.g. in the Journal of Philosophy or some other Journal that is publishing philosophy.