A repertoire means choosing your first move with White and your replies to 1.e4 and 1.d4 with Black. Don't memorise; choose openings whose ideas you understand.
Suggestion: if you like open games, play 1.e4 and the Italian with White; if you like quiet games, 1.d4 and the London. With Black, 1...e5 or the Caro-Kann against 1.e4, and 1...d5 with the Queen's Gambit Declined against 1.d4, are good starts.
After every game, check your opening moves: where did you leave the known path? That way your repertoire grows from real games.