Magento Theme Development
I do not ever buy themes as I want full control over the code I am using. Bought themes offer a lot for a cheap price but they are not optimised well and will always cause issues later on.
Frontend Tools
I use tools such as Bower and Gulp to preprocess SASS and move and files.
Theme Inheritance
I build upon the default RWD theme where I use an infinite fallback structure so that I only need to override certain parts of the template.