Magento – Magento 2 styles not showing after choosing luma theme

You seem to be talking about two different things. In Magento, there are

a) packages
b) themes

The package defines the first folder and the theme the underlying "child" folder. An example:

app/design/frontend/PACKAGE/THEME

Furthermore, you can specify a separate folder for your skin via the backend settings, but it will be in the same package that you configured.

So, say you put package = mycompany and theme = mytheme and skin = myskin,

then your paths will be:

app/design/frontend/mycompany/mytheme/template -> for phtml files
app/design/frontend/mycompany/mytheme/layout   -> for layout xml files, e.g. local.xml
skin/frontend/mycompany/myskin                 -> for skin files like css, js, images

http://alanstorm.com/magento_2_less_css

I like Alan Storm's article. It goes through what a front end developer needs to know about LESS and working with Magento 2 front end.

You're previous answer is correct, and Grunt is a great way to go. "Gulp" is similar and apparently even faster at it's job. It's fast, and you can setup at the very minimum a watcher that watches your .less files and when you save the file in an editor it will automatically compile your changes for you. This is only really useful on your local developer machine naturally and on the staging and production server you need to use the Magento 2 commands.

Grunt is very capable of doing more automation tasks for you such as minify files and anything else you want to set it up to do. I also would recommend a chrome plugin called "Auto Reload" through Chrome or Firefox to your project as it too detects changes (you can make it to your css directory). This way Grunt watches and compiles LESS, and auto reload will reload your window automatically when Grunt is finished. You can have it on a separate monitor.

You can also use an awesome tool for Magento such as PHP Storm. Works really well not only for this task but will also help you develop as you wonder where is this random file (usually XML or a PHP / phtml file). Not only can you click and find the files you can also setup compass (and I believe Grunt) watchers through this tool for further automation.

This may sound like a lot of work and configuration to some of you (did to me) but "Give me six hours to chop down a tree and I will spend the first four sharpening the axe." -Abraham Lincoln I still believe it's better the time spent on using tools that save us time in the long run.