Born in Helsinki, Gustavson started playing basketball in a local club Wartti Basket.
In April 2018, Gustavson committed to Richmond university basketball team.
[2] After a one-year hiatus due to injuries after finishing college, Gustavson turned professional for the 2024–25 season when he signed with Kauhajoki Karhu Basket in Finnish top-tier Korisliiga.
He was also part of the Finland U17 roster at the 2016 FIBA U17 World Cup in Zaragoza, Spain, where he averaged 11 points and 3.7 rebounds in seven games.
Currently Gustavson plays for the Finland men's national basketball team.