Gregor Rungi began playing basketball at Kohila SK. In late March 2025, Kohila SK announced that he had visited Málaga Unicaja’s youth academy to demonstrate his abilities. Before moving to Germany, he represented Rapla’s U16 team while studying and training at Audentes. On 4 June 2026, ERR reported Rapla Korvpallikool’s announcement that he was joining Ulm’s youth programme; his current Instagram bio also links to Ulm. The Estonian Basketball Association lists him at 207 cm. He represented Estonia U14 at the 2025 Baltic Match and was named among the candidates for the U15 national team’s 2026 summer programme. His exact youth squad and competitions remain to be confirmed.
Before moving to Germany in summer 2026, he helped Rapla U16 win the Estonian Cup and take bronze in the Estonian championship.