Tips for a beginner?

play a lot and Watch youtubers' play videos and see how they do it

I mean honestly you can spend a lot of time to play a game and get better but at the end of the day it sort of wasting time. Believe me, I've spent 6 years in this

All the others comments plus: the command /muteall : it will help you to focus on the game and leave away the toxicity of the game and help you to keep the most important part: the fun

Do 3-4 rounds vs AI. After that, play Aram to learn the shop, and learn the champs abilities.
Finally, go 5v5 and focus on one role (I recommend not jungle for new players). After a dozen or so games, you should have an idea as to the expectations of your role, and the roles of others on your time.

You only get better by playing, videos can only help so much. Don't worry if you do bad

Learn the basics, like each champion's abilities, how to farm correctly, what to build with each champion, basic wave control, etc.
/Mute all (optional, but very useful if you care about your mental health lol)
Play a lot of games and watch a lot of League-related content.
And last but not least, if you're NOT playing competitively, try tohave fun, it's a game after all, this does not mean you have to play to lose tho, you can have fun and play to win.

Watch YouTube and Twitch streams and see how other players play.

I found it helpful studying professional games and taking tips from the pro players.

play a lot, learn champions them and most important have fun.

Don't play a champion just because someone says it's really good etc. Just try them all and find your playstyle.

Just wach youtube videos of better players and play more

Play only a few champs and find a role u like pratice killing minions at first wich will really help u in the long run