Stockings was born in Sydney, New South Wales, in 1974. At 18 he entered the Australian Defence Force Academy (ADFA) as an Australian Army officer cadet. Graduating in 1995 with a Bachelor of Arts in History and Politics, he completed his final year of study as an officer cadet at the Royal Military College, Duntroon and was commissioned into the Royal Australian Infantry Corps in 1996. Stockings returned to ADFA the following year to undertake an Honours degree in History, following which he was posted to the 3rd Battalion, Royal Australian Regiment (3RAR) in 1998. With 3RAR he deployed as part of the International Force East Timor in 1999–2000.