To reach Gatwick on a budget, take Thameslink from St Pancras, Farringdon, or London Bridge

https://kylerotul149.trexgame.net/gatwick-airport-drop-off-and-pick-up-rules-fees-and-locations

To reach Gatwick on a budget, take Thameslink from St Pancras, Farringdon, or London Bridge. Trains are frequent, accept contactless and Oyster, and often cost less than express services.