A native of Sylmar, California, Gbewonyo played high school basketball at Kennedy High. He began his college career at College of the Canyons (Calif.), where he earned All-Western State Conference honors and was named the team's Most Valuable Player as a sophomore in the 2000-01 season. He averaged 21 points and eight rebounds that season. After two seasons at Canyons, Gbewonyo transferred to Washburn (Kansas) University, where he was a part-time starter and key component for the Ichabods in 2001-02. He started 14 of 26 games played, and averaged 7.7 points and 4.0 rebounds, as WU advanced to the MIAA Tournament semifinals. He moved onto Henderson (Ark.) State University for his senior season in 2002-03. He averaged 9.0 points and 6.0 rebounds in 35 games for the Reddies, helping them advance to the NCAA Division II South Region finals.