If you want to become stronger at chess, studying tactics consistently is one of the fastest ways to improve.
The average 1800-level player has relatively limited chess knowledge but is strong tactically.
Chess skill is largely based on pattern recognition. The goal is to improve your pattern recognition so that you rarely miss one-, two-, and three-move tactics. Even if an 1800-level player doesn't spot a tactic immediately, their pattern recognition is often strong enough to alert them that a position may contain a tactical opportunity, prompting them to calculate more deeply.
Many players develop tactical strength simply by playing a large amount of speed chess, but studying tactics is a more time-efficient way to build pattern recognition.
Consistency is the key. I recommend 30 minutes of tactical study per day. I know a couple of people who improved tremendously by studying tactics for 60 to 90 minutes daily, but most people don't have that kind of time. Thirty minutes a day is a good goal, but if that feels overwhelming, 15 to 20 minutes per day, done consistently, will still improve your tactical ability.
More than 20 years ago, I spent a year studying 300 Most Important Chess Positions for just ten minutes each night before bed, along with other tactical exercises. After that period of study, I achieved some of my best tournament results.
I recommend repeatedly working through the one-, two-, and three-move tactics on my website. Don't be afraid of repetition; repetition builds pattern recognition. With enough practice, a 2000-level player should be able to complete all of the White-to-move problems in the one-, two-, and three-move sections in about 30 minutes.
White to Move.
Black to Move.
These tactics problems, along with the book Sharpen Your Tactics, helped me improve from 1800 to 1900.
The books 300 Most Important Chess Positions and Practical Chess Exercises, together with the 1,000 problems in the Shredder app—which I enjoy so much that I have worked through them roughly 30 times—helped me improve from 1900 to 2000.