Athens is easy to do by yourself - walk to the metro, which was a pleasant walk taking 25 minutes. There is a good, safe sidewalk, and as long as you keep the water on your left and keep walking past all the ferry piers, you can’t miss seeing the escalator and overhead walkway that lead across the main street to the metro stop. Fare was 0.80 €, and the metro was very efficient since it is not affected by traffic. It takes about 20 minutes to get to Monasterion (Monasteraki) stop which is near Acropolis. 12€ combo ticket gets you into Roman Forum and acropolis. At 7 €, the National Archaeological Museum of Athens is an amazing bargain and this is at Viktoria metro stop.
Have you not gone to that web site I recommended yet??!!!