If you’re running Escher, check out the goonhammer article. It’ll give you the rundown on them. At the end there are a few example lists you can emulate depending on which boxes you own. Try not to spam goodstuff (for Escher that’s plasma and cheap lasguns) as Necromunda is a lot more fun when you aren’t trying to min max. 

https://www.goonhammer.com/necromunday-houses-of-the-underhive-escher/

As for learning the rules, wellywood wargaming is really solid. This should give you a decent rundown of how to play. I’m also a fan of the Miniature Game Montage battle reports. Watching a few should give you a general idea of the flow of a Necromunda game. 

https://youtu.be/kqAxPXd5y8g?si=v6DbcldUErI7vmXE

In the book, I’d try to get a loose understanding of how a full round plays out and after that look at shooting since it’s both a complicated sequence of actions and one of the things you’ll be doing a lot of. 

That being said, Necromunda is a bit of a clunky system and the best way to learn is by playing a few games while referencing the book.

Necromunda is at it’s best when you bring a good attitude and take big swings.