In the summer of 2003, prior to his senior year of high school, Gregory attended Interlochen Arts Camp and took home one of the institution's top honors, The Maddy Award for Excellence in Musical Theater, for his role as the Fairy Godmother in Sweet Charity.
He began his collegiate study at Baldwin-Wallace College (now Baldwin Wallace University), where appeared as Owen in Brian Friel's Translations, Oberon in A Midsummer Night's Dream, and as Creon in Seamus Heaney's The Burial at Thebes, for which he won the theater department's award for Best Actor in a Play.
The same year, he earned his Equity card while appearing in The Full Monty for the now-defunct American Musical Theatre of San Jose.
[citation needed] Gregory's audio Western, "Powder Burns," won the Voice Arts Award for Outstanding Storytelling/Best Performance for an episode dealing with Alzheimer's disease.
In June 2023, David starred as Juror #8 in a sold-out run of Twelve Angry Men at The Powerhouse Theatre in New Canaan, Connecticut.