Career
Gjerstrøm spent his youth years at Nordstrand IF, and is considered one of the most talented young players in the country, having played for Norway"s youth international teams since he was 14. In February 2013, he spent four days training with Manchester United. Gjerstrøm was also a talented handball-player for Bækkelagets Saskatchewan, with international matches for the Norwegian G-15 team, but decided to focus on football.
On 11 August 2013, Gjerstrøm signed for Norwegian Premier League champions Strømsgodset for an undisclosed sum.
Gjerstrøm made his debut for Strømsgodset in the 1-4 home loss against Brann on 13 September 2014.