Gosa was born in King William's Town in the Eastern Cape and attended the East London-based Selborne College. He played first team rugby for the school, also captaining the side in 2013.[2] He was selected to represent his local provincial union, the Border Bulldogs twice at schoolboy level; he played for them at the Under-16 Grant Khomo Week in 2011, as well as at the Under-18 Craven Week tournament in 2013, where he scored a try against Namibia[3] and kicked seven points against the Boland Cavaliers.[4]
After high school, Gosa concentrated on playing rugby sevens. He represented the South Africa Sevens Academy team at several international tournaments in 2014,[5][6] 2015[7] and 2016[8] – and was also named in an extended training squad for the team as they prepared for the 2016 Summer Olympics[9] – but failed to break into the national team.
Gosa also returned to the fifteen-man form of the sport towards the end of 2015, making two appearances for the Johannesburg-based Golden Lions's Under-21 team in the Under-21 Provincial Championship.
In August 2016, Gosa was contracted by the cash-strapped Eastern Province Kings for the 2016 Currie Cup Premier Division.[10] He made his first class debut by coming on as a replacement in their match against the Boland Cavaliers, scoring his first senior points within ten minutes of his debut by converting a Johann Tromp try.[11] After two more appearances off the bench against the Blue Bulls[12] and Western Province,[13] he made his first senior start as the fly-half in their midweek match against Griquas, kicking seven points in his side's 24–47 defeat.[14] He started as a fullback in their defeat to the Sharks[15] before reverting to the bench for their final two matches in a season that saw the EP Kings fail to win any of their matches to finish bottom of the log.[16]
Gosa moved to Potchefstroom to join the Leopards for the 2017 season.