Welcome! League is definitely a lot to learn, but it’s also a lot of fun!
1) When you’re looking for champs to play honestly just start with whoever seems fun to you. The amount of champions can be intimidating, so don’t feel rushed to learn and play them all. Focus more on trying out champs that you find interesting - odds are it will be much more fun to learn with one of those champs than something someone told you was meta. We have a ton of awesome content creators that have guides on YouTube and the like.
1.5) Try not to get too anchored in what’s meta each patch as you’re learning the game. Metas will come and go, but if you build a solid foundation by really focusing on a handful of champs you’ll improve much quicker.
2) Don’t feel like you need to play ranked right away. You’ll see a lot of conversation online around what is / isn’t meta, how to climb, etc. which is great, but we also have way more casual modes that are helpful for learning like ARAM ...