High elo players! What do you think is the most important thing to focus on to gain elo?

I think every players have their own thing that made them climb the ladder. I want to become better at this game, and i'll play euw next season, and my goal is going to be the higher elo brackets, this is why i'm curious what did you focus on while improving the most. You can go into details. Halp plz :(
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