Comments on https://lichess.org/@/neimar24/blog/chess-opening-tips-build-a-repertoire-that-wins/h4yCYHMa
The position in the image is nonsense. Better set up a real position.
Repertoire for black is more important than for white. White can afford to lose a tempo.
As white you can play a black defense in reverse.
The best way to study openings is to study whole grandmaster games.
That also shows resulting middle games and endgames.
Another question about a repertoire is how deep and how wide.
Some variations of the Sicilian Dragon, Sicilian Najdorf, King's Indian Defense Mar del Plata, Ruy Lopez Marshall Attack run 20 moves deep.
If you open say 1 e4, then you want to know what to do after 1...e5, 1...c5 and maybe also 1...e6, 1...c6, but do you also need 1...d5, 1...d6, 1...Nf6, 1...Nc6, 1...g6, 1...b6, 1...a6?
My approach is to just play. Whenever you deviate from the known best move, look it up after the game and deepen your knowledge. Whenever your opponent deviates from what you know, look it up after the game and widen your knowledge.
get comfortable in any position, survey the board to set up threats big or small, no need to overhaul what to learn to beat that one player who plays weird/boring/aggressive because you trust your plan