So where would you start? (greek philosophers).
In philosophy? I would start by reading a few good general historical reviews of Western philosophy. An excellent, lively, and informative one, is by a countryman of yours, Anthony Flew, who is an eminent philosopher in his own right. An Introduction to Western Philosophy
. Another, very eminent philosopher (and countryman of yours) is Bertrand Russell. History of Western Philosophy
. After that, if you are up to it, you can begin to read primary texts. I would not start with the pre-Socratics. I would begin with the famous early Socratic dialogues by Plato. Apology, Euthyphro, Crito, Phaedo
. You can read all of them on the WWW.
Just google them.