During his club playing career, as a member of Žalgiris Kaunas, he won the EuroLeague championship in 1999.

1998 together with R. Javtokas, A. Macijauskas, D. Zavackas, G. Kadžiulis, T. Nagis, played for the Lithuanian youth basketball team.

On 31 August 2016, Giedrius Gustas announced his retirement as a player, and he became the assistant basketball coach of the Lithuanian League club Dzūkija Alytus.

[5] In 2017, Giedrius Gustas graduated from Vytautas Magnus University with a Bachelor's degree in Business Administration and Management.

Two years later, Giedrius Gustas graduated from the same institution with a Master's degree in Marketing and Sales.