I can't begin to tell you anything about the weight of yarns or types of needles, etc. Here in China, you tell the shop keeper what you are wanting to make and they tell you if your yarn will work for that project and how much you will need. They'll tell you the size needles you need to use.
No one uses patterns! It's a "master" driven art . . . you learn from those who have already conquered your project. Knitting shops only hire those who knit. You don't have to pay for a class . . . you just go and sit in the shop and the master will teach you what you need to know. You return when you hit a snag or when you are ready for the next step of the project.
I've not done anything complicated, but I have sat and watched these artists at work. They are truly amazing.
I'm including some photos of my "spectacular" flat objects. Don't ask for any technical details because I won't be able to answer the questions! The names of the pieces are purely my own.