Take care to use the recommended quantity of olive oil; it's important for the end result, and ideally use Greek oil if you can.
Use a red onion if possible; they are available in the summer and are so good raw.
And to drink?
If you like it, why not the famous Greek white wine Retsina? Or a fruity rosé from Provence. To accompany this salad perfectly, drink one or the other, well chilled and in the shade.