He won a gold medal at the 2011 Ivan Hlinka Memorial Tournament and a bronze at the 2012 IIHF World U18 Championships.

[4] Gaunce attended Markham District High School where he played on their ice hockey team registering 4 goals and 21 points in 17 games.

Despite playing much of the season on defence, he was named to the Toronto Star High School Hockey All-Star First Team.

[6] At the end of the season Gaunce was Belleville's nominee for the Bobby Smith Trophy as scholastic player of the year, but lost out to Adam Pelech.

Canucks' general manager Mike Gillis stated that going into the draft they had targeted Gaunce and if he had not been available Vancouver would have traded down to add extra picks.

Gaunce played the entire 2014–15 season for the Canucks' American Hockey League (AHL) affiliate, the Utica Comets.

[9] On October 29, 2015, Gaunce made his NHL debut with the Canucks in a game against the Dallas Stars in a 4–3 overtime loss.

[10] The next day, Gaunce scored his first NHL goal against Anders Lindback of the Arizona Coyotes in a 4–3 Canucks win.

[16] Gaunce quickly transitioned to the larger European ice, recording 5 goals and 12 points and a +10 plus/minus rating in 18 contests.

As a free agent, Gaunce returned to North America in the off-season, securing a one-year, two-way contract with the Columbus Blue Jackets on July 30, 2021.

[18] After three seasons within the Blue Jackets organization, Gaunce left as a free agent and was signed to a two-year, two-way contract with the Minnesota Wild on July 1, 2024.

[3] Team Canada lost its opening game to Sweden 5–1, but finished the preliminary round with a 2–1 record and received a spot in the semi-finals.

[26] Canada re-matched Sweden in the Final with Gaunce scoring early in the third to give the Canadians a two-goal advantage then assisting on another goal mid-way through the period.

[29] After Canada started the tournament with split decisions Gaunce scored two first period goals and added an assist in a 6–2 win over the Czech Republic.