Born in Swindon, Wiltshire, Gilligan joined the Watford Academy at the age of 16 before Northampton Town took over the third year of his scholarship in August 2005 after being tracked by then manager Colin Calderwood.
For the 2007–08 season, Gilligan moved into midfield where he has looked to have found his natural position, here he played regularly in the first-team scoring four goals in 28 starts.
Upon expiry of his contract at Northampton Town in 2012, Ryan joined Swedish club Östersunds FK, managed by ex English Footballer Graham Potter .
With IK Brage going into administration, Gilligan opted to leave and signed a contract with local rivals Dalkurd FF, this proved to be a very good move.
At the end of the season he decided to move back to the north of Sweden and sign with Umea FC a club that had been keen on Ryan for several years.