Great post. I would have to add to it, that once you get the rest of the basics under your hat, be sure to learn regular expressions. Months ago I finally took a week to learn and experiment with them, and they have totally changed my whole automation game. They allow you to extract pieces of text based on set of rules, or run advanced find and replace commands. Many actions in KM let you take advantage of this powerful tool.
In the beginning, I was pretty confused about using them and would spend hours trying to modify a regular expression to work that I found on the Internet. But actually sitting down and learning them from scratch usually lets me condense what would have been 5 or even way more separate actions into one, and often more reliably.
http://regexr.com Was the tool that got me figuring this stuff out with their cheat sheets and example expressions. It is my go to tool for writing a regular expression so can see how it will behave before using it in KM.