The Answer here will depend upon your desired aims in terms of flavor and body. The AeroPress manual suggests a ratio of 1:6 coffee to water. This produces a very intense and concentrated shot that can be diluted with milk or water for longer drinks. If you want to brew something for dilution, this is an excellent place to start.  Alternatively, for a longer drink that you can enjoy undiluted, we'd recommend starting with a ratio of 1:18 or 11g of coffee to around 7oz of water.