[3] At Arsenal whilst playing for the club's academy, Sunu won the FA Youth Cup of 2009 beating Liverpool by 6–2 on aggregate in both legs of the final.

[6] He made his first team debut for the club when he started a League Cup match against West Bromwich Albion on 22 September 2009, playing 58 minutes before being substituted for Carlos Vela.

[7] On 9 December 2009, Sunu made his UEFA Champions League debut in Arsenal's 1–0 away defeat to Olympiacos, coming on for Jack Wilshere on 76 minutes.

[11] After scoring in the final of the 2010 UEFA European Under-19 Football Championship in July, Gilles suffered a cartilage injury in his right knee that would keep him out of action for two months.

After rounding Lens goalkeeper Vedran Runje, Sunu flicked the ball back from the byline for Kevin Gameiro to head in from five yards to make the score 2–2.

[17]Gilles Sunu signed a four-year contract with Lorient on 31 August 2011, just three days after being an unused substitute in Arsenal's heavy 8–2 defeat to Manchester United.

[20] Sunu scored his second goal of the season in the quarter-finals of the Coupe de la Ligue of 2012 in the 1–0 away victory to Le Mans.

Gilles beat Le Mans goalkeeper Giorgi Makaridze at the near post on the 70th minute after coming on as a 62nd-minute substitute for Innocent Emeghara.