Billis played from a young age with the youth teams of Panionios, before he started his pro career.
Billis signed his first professional contract with the Greek Basket League club Panionios, on 2014.
After playing one season with Kolossos Rodou,[1] he returned to Panionios for a second spell on July 28, 2016.
During the 2019–2020 campaign, Billis played with Karditsa of the Greek 2nd division.
On August 2, 2022, he re-signed for another season, his sixth overall with the club, and was named vice-captain in the process.