Getting to 'mastery' is going to take a lot of effort, time and work. You can't become an expert by simply reading tutorials - the best way is to learn by doing. Get to grips with the basics, then play around. Once you're more comfortable, invest in some books.
If you're looking to build a complex system then you might be better using an off-the-shelf alternative. Try Googling around for various e-commerce systems (Magento is in vogue at the moment) and Content Management Systems (CMSes) before you decide to reinvent the wheel.
