[3] He won gold in the flyweight event of the 2013 European Youth Championships in Rotterdam, defeating Masud Yusifzada of Azerbaijan in the final and taking home the Best Boxer Award.

[2] Cully was defeated by future pro stablemate David Oliver Joyce in the quarter-finals of the 2016 Irish Elite Championships which ended any hopes of attempting to qualify for the Rio Olympics.

[9] A busy start to his pro career saw Cully then fight twice at the SSE Arena in Belfast, scoring impressive wins over durable Englishmen Josh Thorne and Kane Baker.

First he would score a statement third-round stoppage over game Wearsider Jordan Ellison on 5 October 2018 at the Titanic Exhibition Centre before knocking out Tanzanian Mohammed Kambuluta (18–5, 7 KO) in the first round at the same venue on 7 December 2018 to improve to 7–0 as a pro.

[13] After months of looking for a challenger for the Irish lightweight title,[14] he finally won the vacant national belt on 1 February 2020 when he faced unbeaten local prospect Joe Fitzpatrick (10–0, 7 KO) at the Ulster Hall in Belfast.