Next opening to study

@hampy #1
Focus on slow time control games first if you want to improve : rapid, classical, correspondence chess on Lichess.
Your opening choices sound very fine and solid. Excellent !
Also, to improve you must find a good balance between training/studying, analysing your own games and playing.
Especially at lower ratings level it makes sense to focus more on analysing and training and less on playing.
Avoid bullet chess until your slow time control ratings go over say 1800 - 1900 (to avoid playing for cheap tricks and speed, and to avoid anchoring mediocre and superficial chess ideas).

Good luck, have fun !

1) What do you play against 1.d4 , 1.c4 and 1.Nf3 ? Maybe the next opening you need to learn is a reply against one of those moves as Black.

2) In my opinion, the London system looks easy but is actually best left for players with a lot of chess culture. It's like the Modern Defence as Black. If you play it on auto-pilot, you might loose without knowing why against the antidote lines. Gata Kamsky manages to overcome that problem, but we are talking of a former 2700+ candidate.

So with White, try as much of the Queen's Gambit as you can, vary your approach (with cxd5/Nge2, with cxd5/Nf3/h3, without cxd5,...) and see what you like. Against Indian Defences (1...Nf6), try to get a Queen's Gambit structure (or something related to it) :
1.d4 Nf6 2.c4 e6 3.Nf3 d5 4.Nc3 or 3.Nf3 b6 4.Nc3 Bb4 5.Qc2 and soon Bg5 ;
1.d4 Nf6 2.c4 g6 3.Nc3 d5 4.Nf3 Bg7 5.Bg5 Ne4 6.cxd5 Nxg5 7.Nxg5 e6 8.Nf3 exd5 ;
1.d4 Nf6 2.c4 g6 3.Nc3 Bg7 4.Nf3 d6 5.Bg5 0-0 6.h3 .

3) Stick to the Caro-Kann as Black against 1.e4 and try all the variations to see which one you prefer :
1.e4 c6 2.d4 d5 3.Nc3 dxe4 4.Nxe4 and now 4...Bf5, 4...Nd7 and 4...Nf6 5.Nxf6 exf6 (or 5...gxf6).

4) Summary : start from your pool of knowledge, explore from there and "know thyself" :) .

@achja @A-Cielbleu
Thank you both for your extremely helpful and encouraging responses.
You've given me a lot to think about!

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