To avoid crowds, travel off-peak when heading to Gatwick

https://www.scribd.com/document/1077066259/Heathrow-to-Gatwick-Airport-Transfers-Coach-Taxi-or-Train-174457

To avoid crowds, travel off-peak when heading to Gatwick. Midday trains and late evenings are usually quieter, with a better chance of finding seats and space for bags.