It depends on your chess goals. Are you trying to win against one of your chess friends? Are you trying to prepare for an in-person tournament? Are you just trying to improve at chess as a hobby? etc.
Your reason for playing chess will be a factor in how to best gain rating for you.
If you want to improve more overall, then the process is not a fast one. You learn solid openings and don't focus on short-term rating swings. You play to learn and analyze your games to try to minimize your errors in the future.
If you are more on the hobbyist side, then sometimes learning unsound gambits and solving lots of chess tactics puzzles (for gaining pattern recognition) can help you a ton, but eventually silly gambits stop working against studied opponents and then you'll have to go back to learn what you should have learned in the first place.
This is an example. I don't hate all gambits. They have their place and can even be used to help teach concepts like "initiative" or the value of material, but if you want real chess improvement, then the "get lots of elo fast" mentality is the wrong mindset.
how to get lots of elo fast