He gained a Bachelor of Education in special education and in social-community education.
He is a former leader of the National Union of Israeli Students. During his national service in the Israel Defense Forces he became a sergeant major. In the 2013 elections he was elected to the Knesset on the Labor Party list.
Still serving as a reservist in the Armored Corps, he had to miss his first planned speech in the Knesset after being called up for reserve duty in his tank unit
He joined 34 lobby groups, chairing eight of them, including the Lobby for Lone Soldiers. On 31 July 2015, after a stabbing at the Jerusalem gay pride parade, Shmuli came out as gay.
He was the only open gay MK until Amir Ohana from Likud was sworn in as the replacement for minister and MK Silvan Shalom, who resigned after a sexual harassment scandal.
During his first term in the Knesset he was a member of the Economic Affairs Committee and an alternative member of the Special Committee for the Equal Sharing of the Burden Bill and the Special Committee for the Enforcement of the Security Service Law and the National-Civilian Service Law. He was a member of seventeen lobbies, chairing eight of them, including the Lobby for the encouragement, strengthening, and support of discharged soldiers and the Lobby for the Fight against 'Price Tag' Acts and the Prevention of Harm to Israel Defense Forces Soldiers. He took the third spot on the Labour Party list in primary elections held on 13 January 2015, which put him to the fifth spot on the Zionist Union list for the 2015 Knesset elections In his second term in the Knesset he became chair of the Subcommittee for cruelty towards animals and a member of six committees, including the Education, Culture, and Sports Committee and the Labor, Welfare and Health Committee.