Gilles previously served as the member of the National Assembly for the 5th constituency of Bouches-du-Rhône from 2002 to 2007.

Gilles held the mayorship of the 3rd sector of Marseille, which encompasses the 4th and 5th arrondissements, from 1995 to 2017.

In 2008, he was elected to the Senate on the Union for a Popular Movement list led by Marseille Mayor Jean-Claude Gaudin.

[4] In the party's 2017 leadership election, Gilles later endorsed Laurent Wauquiez.

Since 2022, Gilles has been leading Édouard Philippe's Horizons party in Marseille.