Learn opening principles first so you at least understand the why behind each move. Develop your pieces, control the center, get your king to safety. If you are starting out, I recommend the Italian as black and white, and the Queen's Gambit Declined in response to d4.
OPENINGS AND DEFENSES
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You are ~800 rapid and blitz, no? There are plenty of chess YouTubers to help with openings as well as the lessons here on Chess.com, but realistically there's no substitute for just playing the game. Opening principles are good to keep in mind, but don't stress about them. If you blindly follow them, you'll never learn why they're so useful, you won't know how to play against them, and you won't develop creatively. Use opening principles, but if you have an idea, play it, and whether it works or not, analyse it after the game to find out whether or not it was a good idea.
My recommendations are as follows.
White highly aggressive openings: Scotch Game (take on c6, Qf3 in the Intermezzo, Bd3 and castle if bxc6, take the queen Bd3 and castle if dxc6), Scotch: Goring Gambit (develop quickly and start attacking).
White mildly aggressive openings: Ruy Lopez (early c3, castle, bring knights to f3 and g3, open the center and start attacking the center and the kingside) Bishop's Opening (d3 Nc3 Nge2 0-0 f4)
White passive aggressive openings: London System (try to trade DSB on g3 to open the rook, castle queenside, Qc2 Bd3 g4 and murder the kingside)
Black against 1. e4: Choose between Caro-Kann, Alekhine's, Modern, 1... e5 (Petrov's if possible), Pirc.
Black against 1. d4: Choose between KID, OID, Modern, Budapest Gambit.
I am a new chess player. Where do you find and learn all openings and the best defenses?