Playing against e4 as black
Based on your playstyle. I personally played only french, caro, sicilian and de smet gambit system. I knew basically nothing about the sicilian and played it like a system
Pirc / Modern / KID or something with fianchetto is awesome U1000.
You get familiar with having a plan (give space advantage to opponent, counter with tactics later)
pretty simple moves that you can play against everything are nice... So watch Yasser Seriwan or some Cuban National Master I forgot his name there are some nice vids about the Pirc.
Also try to mess around with e5 from time to time and check out the series "Building Habits" by Aman Hambleton . It's brilliant for beginners because it teaches principles... He basically recommends - "2 knights against everything then follow principles" without calling it a specific name or following too much theory... He also does give exceptions for example if White goes Vienna we develop our Bishop to c5 like "bishop's opening" with Black, thus breaking the princple of "knights normally develop before bishops", and there is a concrete reason (see in video).
But that in itself is vital and something many beginners don't get... At some point around 1000 you will start accumulating these exceptions which are important you will understand you can't play the same thing against everything, and e4 can lead to a million different stuff which demands different responses...
So If I were you I'd explore both directions... Pirc as well as e5 and then switch exclusively to e5 or Sicilian or Caro when you are 1000. Those are the serious openings and once you study them seriously at around 1200 you don't need to change anymore pretty much ever...
What should I play against the most popular e4 openings when i am playing black? I am having a struggle finding an opening i enjoy. If possible I would like to know if there are any good gambits. I am 750 elo