Both destinations are served by Dharamsala (DHM). Since there's no flight route between them, the best way to travel is by road.
Khajjiar
Fly to Dharamsala (DHM), then travel by road to Khajjiar. Taxis, buses, and private cabs are available from the airport.
Dharamsala
Fly to Gaggal (DHM), then travel by road to Dharamsala. Local transport options include taxis, auto-rickshaws, and state buses.