personal best strat to get better at chess

Forget elo.

i quited my day job

Rapid till 1600 then grind 3|0 blitz (you don't have to do this)

The other strategy is get good at everything

Personally the Caro Kann and the Italian openings have got me to a point where I'm more confident in the middle game. Learn a couple of openings so you can focus on the middlegame properly. Endgame study is important too. I started the year around 1000 rapid and now I'm at my my highest rating 1480. Most of that progress I relied on the Caro Kann :P :_(

The IMHO best puzzles on chess.com are actually the puzzle rush. The third type, without time control, but after 3 wrong answers you're out. That really puts a lot of pressure to find the correct answer. The first ~20 puzzles are basically for free (mostly mate in 1 or 2). Then it ramps up, and keeps ramping up. Unfortunately after 40 puzzles or some such it just gets too damn hard for me. Still, you can get it again the next day.

Lichess.com is okay to get a lot of more or less easy puzzles. The interface is the best of all choices, too. You dont get told what you're actually looking for. Its mostly wins though.

But my favorite so far is simply called chesspuzzles.net - it starts off quite hard and has some pretty tough ones in the mix. Unless you keep failing, then it scales down. And it has for example draw puzzles. Unfortunately it explicitly tells you if thats what your're looking for.

I also found a chess interface that comes with a lot of training. Its called Lucas Chess R. I bet other such chess interfaces have compareable sets of training data.

Play 15|10 rapid and use all your time.
Blunder check before you move.
Whenever you lose a game, analyse it.