The items below are really all you need when it comes to getting started with calligraphy! I've listed my recommendations for newbies, with links to buy them on Amazon, John Neal Booksellers and Paper & Ink Arts. These are the best options and won't break the bank but are of a really good standard. You'll probably already have a ruler at home and some paper to play around with, but if you're serious about practicing or getting better than just “decent” results, I highly recommend at least getting some basic paper that works well with ink. Nibs are listed in a separate section below.
Perfect for measuring line height when drawing guidelines
These are my recommended nibs for those just starting out. There's a whole world out there and other people will have other suggestions, but between these choices I think you'll be able to find something that works for you!