Learn about databases (MySQL and MongoDB), but take your time. Learning simple queries and basic design will be good enough for now.
Again, readability and maintainability (that includes testability) are the most important part of writing good code. After that it's elegance and efficiency. Do not repeat yourself, and ensure that every class and method/function you write only does one thing.
And as always, ensure that you understand each convention that you adopt, so you know why you are doing what you do.
Once you learn to code, the more important thing is to learn how to think and how to design great systems and how to architect good code (code that's readable, maintainable, and efficient).
PS: post your code to GitHub as you learn, so you can look back at all the different versions, and can build up a "body of work" on the site. Ask questions on Stack Exchange (though be careful, their feedback may seem rude to you) to get your account going there. Stack Exchange also has a code review section that you can post code to for review ( http://codereview.stackexchange.com