From Croydon, hop on Southern or Thameslink from East Croydon station

https://deanfvtf623.lowescouponn.com/thameslink-to-gatwick-direct-routes-through-central-london

From Croydon, hop on Southern or Thameslink from East Croydon station. Trains to Gatwick are frequent and fast, often taking less than 20 minutes platform to platform.