openings

You've had this account since 2017, but since you've played less than 1000 games on here (and most of them bullet/blitz), these resources might be useful for you:

First, of all, there is no "best opening" pragmatically. It is about preference, play-style and what openings you are comfortable playing; just pick a solid opening or two you like and stick with refining those. 

Before getting deep into any opening though, I recommend chess opening principles: 

https://www.chess.com/blog/KeSetoKaiba/opening-principles-again 

Even when you decide on an opening, you'll still likely utilize these foundational principles. 

Next, maybe check out this video by IM Levy Rozman @gothamchess about openings to choose by rating. I don't agree with every decision he recommends, but I respect this opinion enough to recommend the video; his opening choices look good enough for practical play:

Best Defences for black are probably 1 e4 e5, 1 e4 c5, 1 d4 d5, and 1 d4 Nf6.

Especially the Berlin, the Sveshnikov, the Slav Defence and the Grünfeld.

Thanks for your tips, I'm only just starting to get into chess properly now. 

Glad to help

As for the openings @tygxc mentioned, I personally like them as well, but it is more about personal preference and what you've studied.