What are good openings for 300?


any one that you want to play. Some are more complicated than others but they all have some level of theory. But at your level, the probability that you will actually see anything even close to theory is almost ZERO. Play, learn, study, and have fun! it's a game, enjoy it!

Learn them, try to apply them and check afterwards if you could have applied them better.

Two very good books for you to read at this level are Bobby Fischer Teaches Chess and Ruben Fines The Ideas behind Chess Openings. the Bobby Fischer book will teach you tactics and positional patterns. The Ruben Fine book will teach you proper development in the opening and the reasons why you should develop in a consistent manner.

Reach at least 800-1000 only using opening principles. Then learn something simple like the kings indian setup and play it. When you are 1400-1500 you can create an opening repertoire.

At 300 rating, chess openings don't matter as much as following chess opening principles matters: https://www.chess.com/blog/KeSetoKaiba/opening-principles-again
Chances are that both players will make several mistakes in the game after the opening, so you'll be at a nice advantage if you can just navigate the opening fairly safely and then try to capitalize on mistakes you notice from your opponent.
When you do start thinking about an opening, then this video I made can help with that:

Anna Cramling's Cow Opening is not "solid"...it just isn't losing as quickly as some other silly openings like the Bongcloud Opening.

@RoadOcean -
You might find something of interest in my comments/recommendations (#17 & #21) for openings in the following forum thread (particularly for the lower rated improving chess amateur)...
Basic openings for 900...
https://www.chess.com/forum/view/chess-openings/basic-openings-for-900?page=1
Otherwise...
Chess Openings Resources for Beginners and Beyond…
https://www.chess.com/blog/RussBell/openings-resources-for-beginners-and-beyond
https://www.chess.com/blog/RussBell

Anna Cramling's Cow Opening is not "solid"...it just isn't losing as quickly as some other silly openings like the Bongcloud Opening.
Cow Opening in Chess: A Novel Creation by Anna Cramling...
https://www.chessjournal.com/cow-
Bongcloud Attack...
https://www.wikiwand.com/en/Bongcloud_Attack

No openings at 300. Learn basic chess principles and the piece value of the pieces and play e5 against e4 and D5 against d4 as black and always play e4 as white

My suggestion to 300 elo players in playing white is The Ruy Lopez Opening and as black Caro Kann is a good one.

Put pawns in the center of the board. Get your knights and bishops off their starting squares. Castle. Don't leave any pieces unprotected.
At 300, that's all you need to know for openings.
(An opening book I learned a good deal from when I was starting is Mike Basman's Chess Openings.)