Originally Posted by
lhrsfo
From Earls Court to LGW, a more economical and probably just as fast a way is one stop (or walk) to West Brompton, then London Overground two stops to Clapham Junction then the train (one stop) to Gatwick. You avoid Zone 1 altogether and it's more direct.
£18.90 for a through single ticket from Earls Court to Gatwick Airport. It can be made cheaper by splitting tickets and using Oyster part of the way but this is not necessarily something a visitor would be confident doing.
Edit: on further investigation there is
this ticket for £11.30, if you can find someone who'll issue it.