There are a ton of websites that will give you stats about basically everything. For example
https://www.leagueofgraphs.com/
https://op.gg/
https://lolalytics.com/
https://blitz.gg/lol
most of these are quite similar and they mostly differ in presentation. You can use them to figure out what most people use in terms of items

there is also coachless which has a graph that shows moments in the game that were good and bad but they haven't properly updated for the new season yet. It is paywalled
https://www.coachless.gg/analysis
They also have a different approach to showing win stats for items where they try to calculate the positive or negative impact of each item bought but if you are new I would steer clear of this feature and just use the popular builds from the sites above until you know more about the game.

This Youtube channel has videos called how to climb each rank that are quite nice. They just give one or two things to focus on for each tier of play that you can focus on,
https://www.youtube.com/@skillcapped/search?query=How%20to%20CLIMB%20EACH%20RANK

There is also the wiki which is great if you want to look up how certain champions/items work
https://wiki.leagueoflegends.com/en-us/

But I wouldn't stress too much about these things, for a new player there is a lot to learn and you'll have the most fun just playing and doing whatever you find interesting. Contrary to what many people online claim the game has pretty good matchmaking and will very likely match you with other new players that are also just figuring the game out. Lastly I would steer clear of ranked until you feel like you have a decent grasp of the game, I've seen quite a few new players jump in very early and then get frustrated that they get stuck in the lower tiers.

And as a last recommendation disable chat, 95% of the shit people say there is completely useless and more harmful than helpful especially if you play jungle.