Real beginner (700?)
I recommend watching john Bartholomew utube videos on chess fundamentals. there are 5 in the series. As a beginner you will probably lose many games to undefended pieces that are being attacked or can be easily attacked. You've identified some basic principles so practice applying these but also making sure your pieces are coordinated so they defend each other. It is difficult to improve past a point until you have developed the habit of coordinating your pieces. Many of your opponents will also be beginners with undefended pieces so a good middle game strategy might be to look for this and coordinate an attack on these.

Yeah, good advice already.
You have to play a lot to gain experience with how pieces move... obviously you know how pieces move, but you know what I mean, that sneaky bishop hides in the corner then captures your rook. Or your opponent moves their knight to where you can capture it for free, and you don't notice. You just have to play enough games that you can consistently start catching this stuff. Make sure the time control is long enough that you have time to practice this.
Then yeah, opening principals, tactics, all that good stuff.
And I agree John Bartholomew's fundamentals series is very good for new players.
Good luck!

Why would players need to be in ideal psychological condition to play chess? If I am depressed, I play more. Yes I lose more but playing chess helps me during periods of depression. Everyone... Don't worry about ratings.