Any advice on my first PHP website design?

Hello all,
I'm a internet hobbyist and have skill with HTML4 and CSS. I've built a few static websites in the past. Recently I decided to upgrade my skills and learn PHP, more like LAMP. It's been a roller coaster ride ever since! I now find myself reading about SQL query language, htaccess & mod-rewrite, MVC, AJAX, and JSON.
I guess what I'm trying to say is I'm a little overwhelmed at the moment. Too much too fast I suppose. So I decided to just jump right in and make mistakes - lots of them. I started by setting up a WAMP laptop. Now I'm just writing PHP snippits and testing from localhost. I've been coding stuff like text and numeral validators, a CAPTCHA script, built a few variable dump scripts to help with debugging, I've been playing around uploading jpegs to folders in my htdocs root. Just getting a feel for the language while trying to produce some good code tidbits to use later on.
My question is now that I'm getting ready I don't know where to start or how to start? I think I should design the HTML and CSS first. Then I suppose you could produce bare-bones functioning PHP and interleave it into your HTML??? MVC confuses the hell out of me but I do like the idea of one controller script. And while I still don't have a grasp on true MVC I think I will try to use a controller script. There has to be some logical order to go about so you don't end up with a huge HTML,PHP,MYSQL spaghetti code mess that I'll never be able to update 6mo later. Please help.