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

https://cristiansdvt510.fotosdefrases.com/gatwick-airport-terminal-transfer-shuttle-and-walking-routes-1

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.