An attacking midfielder, Bruna spent five years in the youth set-up at Real Madrid from 2002 to 2007. At the time, Bruna was considered hugely promising and even called "the Messi of Madrid".
In the summer of 2007 Bruna moved to England to sign for Liverpool, having been offered and turned down a professional contract by Real Madrid.
"My father agreed with me that moving here would be a great opportunity. I already knew about Liverpool from the Champions League, the final we won and the final we lost. These games, as well as the Chelsea semi-finals, made a big impression on me." A left-footer with a talent for set pieces, he learnt his trade with the reserves, helping them to win the Premier Reserve League in 2007–08.
The longer Bruna stayed at Liverpool, the less the club liked him and finally he was released. Bruna then joined Championship side Blackpool on a two-year deal, with an option for a further 12 months, on 17 July 2011. He made his competitive debut as a substitute in the League Cup defeat to Sheffield Wednesday on 11 August 2011. He made his Football League debut in a 2–1 defeat at home to Nottingham Forest on 22 October, coming on as a late substitute. Bruna also played against Burnley away. Other games for Blackpool included a League Cup tie vs Sheffield Wednesday and FA Cup game again against Sheffield Wednesday.
Bruna was released by Blackpool on 9 May 2013.
On 20 September 2013 Bruna joined SD Huesca, freshly relegated to Segunda División B. Gerardo Bruna played 17 games for SD Huesca, scoring one goal.
Bruna played in a number of pre-season friendlies for Tranmere Rovers, before picking up an injury. He was then offered a one-month contract by the club He made his debut for the club as a substitute in a league cup match but was not offered a long term contract
Bruna signed a one-month contract with Whitehawk, who then played in England's 6th tier, with the option to extend by the club depending on performances. The signing of Bruna was described as a "massive coup" for Whitehawk as Bruna had previously played for clubs such as Real Madrid and Liverpool. Bruna scored his first goal for Whitehawk in a 5–1 victory over Chelmsford City. That was the second goal of his competitive career, the first having been scored for SD Huesca, as mentioned above.
In January 2015, Bruna joined League Two's Lancashire club Accrington Stanley. He scored his first goal for the club in a 2-1 loss to Bury in the Football League Trophy on 1 September 2015. On 18 January 2016, Bruna signed a pre-contract with Canadian club Ottawa Fury which would have him depart Accrington Stanley at the end of the season.
On 15 February 2016, Bruna was released by Accrington Stanley, allowing him to join the Fury in time for the start of training camp.
Bruna has represented both Argentina and Spain at youth level. In May 2008 he was a member of the Spanish under-17 squad European Under-17 Football Championship in Turkey. He made one appearance in the group stages as a second-half substitute in a 3–3 draw with France at the Mardan Sports Complex, Aksu, Antalya. Bruna represented the Argentina national under-20 football team at the 2009 Toulon tournament.As of match played 1 September 2015.