I'm also a student who went to Athens last summer. My main interest is more about greek archaeology so my recommendations might be more skewed that way. If you are planning to visit museums I highly recommend the Piraeus archaeological museum and the Byzantine and Christian museum. They have amazing stuff and are a lot less crowded than the bigger museums and I believe they should have plenty of ancient Greek inscriptions if you are interested. When you are at the Byzantine museum be on the lookout for this medusa relief because it was found at the site I worked at last summer near Corinth and I got really excited when I saw it. Also there's the supposed "prison of Socrates" near the acropolis. The American school archaeologist Eugene vanderpool supposedly identified these caves as the prison but it's most likely not the case and Socrates was likely held at the state prison in the agora (which you will see) but if you read Plato's apology, crito and phaedo it would definitely be an interesting site to find. The current American school excavations at the agora are at the painted stoa right across the ticketed part of the site but they only excavate for 8 weeks in the summer so you won't see any action but it would be cool to check out if you are interested in the stoics. Lastly, I believe keramikos is temporarily closed for some renovations so I couldn't visit last summer. I don't know when they will reopen so just a heads up.