Gashry was the son of Francis Gascherie, perfumer, of Lamb's St, Stepney and his wife Susanna.
Wager brought Gashry in as Member of Parliament for Aldeburgh at a by-election on 30 March 1741 and promoted him as a commissioner of the navy in 1741.
At the 1741 British general election Gashry was returned unopposed as Wager's candidate at East Looe on the interest of Edward Trelawny.
Through his wife, Gashry succeeded to manor of Rotherhithe, and to Kilmenath, near Looe, when Wager's widow died in 1748.
As director of the South Sea Company and Treasurer of the Ordnance, he was consulted by Newcastle on financial matters and subscribed to Government loans.