Take any NJ Transit train from Penn Station to Secaucus Jct. and transfer there to either the Bergen County Line or Main Line if you're going further north than Glen Rock (Ridgewood, Hohokus, Ramsey, etc.). Cheapest way to Penn Station is by Airtrain from your terminal to Jamaica Station and transfer to the E subway to Penn Station, total for Airtrain/subway is $7.25. Your NJ Transit fare depends on how far you are going.
Take any NJ Transit train