There's no universal opening that's good for everyone, each person finds an opening that speaks to them. The opening that's helped me improve most has probably been the French Defense, as I've been playing it for as long as I can remember. However, switching from d4 to e4 has helped me gain rating more recently for the simple reason that I found myself much more satisfied with the position I was playing.
If you are steadily improving, I think you will get to a point where your openings simply can't take you farther because you're not getting enough out of your position and you need more knowledge. For me, this knowledge came in the form of a course on various lines of the French and a switch from a Queens Gambit to an Italian and Closed Sicilian repertoire as White.
Id say that every opening you study in depth and play for a while to have a lot of sample middle games and endgames and the possibilities of each variation helps with improvement. Every different thing you work on widens your horizon and makes you better at something. There is no specific opening rather than just studying new things.
I think the Ruy Lopez has helped me improve the most so far.
This topic has been archived and can no longer be replied to.