Agaba was born in Kabale, Southern Uganda, before moving to the Transkei and then East London, where he attended Stirling High School, where he took up rugby.

[2] In 2007, he was included in the Border team that played at the premier South African high school rugby union tournament, the Under-18 Craven Week held in Stellenbosch.

[2] He returned to the Eastern Cape in 2012, where he joined the Port Elizabeth-based university side NMMU Madibaz for the 2012 Varsity Cup competition.

[8] He started eight of the fourteen matches that the Eastern Province Kings played during the round-robin stage of the competition and scored a try in their 63–7 victory over the Griffons.

[16] He started their 25–45 defeat to Griquas a week later[17] and also their final match of the campaign, which the Eastern Province Kings won, beating the Pumas 26–25 to secure their only victory in the competition.

Despite a 5–12 defeat in this match,[27][28] South Africa still finished top of Pool B to set up a quarter final rematch against Australia, with Agaba named as a replacement in his side's 22–5 victory.