In my opinion Sona is one of the best supports. Her play style is mostly benefited from stacking CDR and Mana Regen, allowing you to spam your spells, thus enabling you to use your power cords more often.

You could also skip Athene's Unholy Grail if you feel you are being focused, or dying to fast in general. If you do not purchase Athene's I suggest getting Aegis of Legion, or Frozen heart. After you choose one of these items the rest is yours to choose.