make a website like Neopets

you'll need to know HTML, CSS, PHP, and other stuff like that. practically, everything. and obviously you haven't played much, or you would know that there are over 100 people in the TNT staff. maybe even 1000.

make a website like Millsberry

U should learn HTML. it's a form of coding to make websites. CSS? Learn that too; it beautifies websites quite a bit. These two are essentially languages that computers understand; they tell a computer what to display in a web browser.

Don't even think about trying an interactive website like that until you've got the basics down pat. With HTML and CSS, you can create a static website: one where users can only observe, not 'do' things like play games, collect virtual money, and so on.

Done that? PHP is a programming language that is vital to making the kind of website you're aiming for