Still a beginner, but getting a little bit better every day. It seem they're a lot of people stuck at below 1000 rating. I can tell you my journey from 900 to 1300 in 3 months.
Opening: First I recommend starting with the Catalan opening, but playing NF3 first move order. Just a solid opening system you can use against almost every defense. Open up the center once you have greater development and attack on the queen side. As black I started with what I call the shadow defense. I just try to keep the game as symmetrical as possible. You'll fall into traps at first, but you'll learn to avoid them. As I improved my tactical ability I switched to E4 opening. I still play the shadow defense.
Constant improvement should be the goal. I treat every loss as a learning opportunity. My theory for losing is that I simply wasn't good enough to win that game. And I need to improve before I'm allowed to play again. If I lost in the opening, I study up on the opening. If I lost in the middle game; I practice tactics and study up on positional chess; if I lost in the end game, I practice end games.
Warmup before every game. I'm currently playing the Italian game, so I bought a book on chessable called thematic chess: the slow Italian. I review a few tactics, learn one new one, and review again. Then I'm ready to play. My point is, if you want to improve you need to be doing more than just playing chess. But again, I'm still a beginner, so take what I say with a grain of salt.
