Are there any good, relatively uncomplicated d4 openings that at good for beginners at all? Something with not too much theory or complicated opening lines that I can use to start getting used to this opening in games?
I'm thinking as white, but also interested in good recommendations for black responses as well...
Jobava London. However I would also advise you to experiment with 1.e4( I generally think it's good for beginners), you have to study a bit of theory but that's okay, you'll most likely get a playable Middlegame.
I want to improve beyond beginner so what should I do... Invent my own brand new openings based on the key principles?
Studying openings will get you almost nothing. If you want to improve, you should study tactics 90% of the time, with a bit of middlegame strategy and endgames thrown in.
That is, if you already know and follow opening principles. If you don't, you should probably start with looking up those.
Well I think this is one of the most misunderstood concept in chess.
When we talk about " Not studying openings as a beginner". It gives them an image that they shouldn't even look at the Openings.
What that statement really means is that beginners should not study openings deeply like GM's do with chessbase and stuff like that.
Beginners should definitely look at the variations and 6-7 moves of opening whichever they are playing. Key manuvers and ideas in the middlegame they get. They should have a " Loose opening repertoire" to work with.
Tactics are the most important aspect of chess and should be done frequently. Because one tactical shot can end the game.