openings

Beyond what many think... 95% of the openings are playable below an Elo of 2500... to the 99% of us.... this means the sky is the limit as far as openings (because none of us are going to get to 2500 elo)

With that stated.... Learn a system, then branch out, adding to it.

By doing it this way, you learn how to use the pawn formation and the typical tactics and strategy behind piece deployment.

You will also want to pick a system that can resist your opponent's attempt at disrupting the development of your pieces and pawns. By doing this, it will allow you to get familiar with the themes and plans of the system. ( you won't be looking at a different position every game)

Doing this will free up time for you to study tactics and develop your endgame technique. Don't worry about playing super optimal lines looking for an opening advantage, just make sure the lines you play are equal and you understand what is going on. Be creative, look for ideas you can call your own in these lines... Why? Because this is where your wins always come from no matter what Elo.