This page explains a variety of basic principles. If you learn everything on this page and edit patiently, you'll avoid at least 95% of the trouble new users have.
"Getting around the site" provides an analogy to help you try to understand the site's structure. This may help you understand why no one replies when you leave messages on your talk page, or why you get in trouble if you leave messages in articles.
"Things everyone should know (and can get into trouble for rejecting)" explains some social contracts that the Wikipedia community has agreed to. The subsection "Some experienced tips" are things that even some experienced users occasionally forget but are good to try to remember. These notes are just my summary of some different site principles, they are not policy.
"Finding sources" explains how to find sources -- you do not need to be a librarian. If you can find this site, you can usually find some sources for many topics.
"How to write articles that won't be rejected or deleted" explains, well, how to write articles. Ever since I started following these steps, none of my article have even been nominated for deletion.
"Summary of various site policies and guidelines I use selections of when welcoming most new users" summarizes almost every policy and guideline you might ever have trouble with. These policies and guidelines are not magical invocations that will automatically win your argument (no one "wins" here anyway). There are a few, rare assholes users who might use misquote even more obscure guidelines to try and "win" but that approach is not welcome (that said, a reasonable case that reflects policies very well is more likely to win than an emotional case with no connection to policy). This section is just my summary of these policies and guidelines and does not touch the manual of style -- my summary is not binding on anyone.
"Formatting" explains how to use Wiki mark up. Wiki mark up may look intimidating but you do not need to know anything about "programming" or "coding" or other "computer stuff" to learn it. Think of it as just a few extra grammar rules. If you already know anything about HTML (even if you just took an intro course a decade ago), you're in luck -- Wiki mark up is the fetal alcohol syndrome-afflicted, lead paint chip eating, sibling-cousin of HTML. You may want to look at Help:Cheatsheet as well.
The table of contents is automatically generated because there are enough sections to necessitate one.