Lettering for lefties can be tricky. Whether you're interested in formal pointed pen studies or are jumping into a more creative modern calligraphy route, I would suggest you study the righties for mechanics but know that you're going to have to come up with accommodations that work for you.
I have a set of antique nibs that belonged to a cousin who studied Zanerian. I've been told that he was a lefty, but the first time I tried his righty oblique holder... well, it went right back into the drawer.
Those beautiful Tombow Dual Brush Pens? The ones available in 96 brilliant colors? Those aren't for you right away. Buy now and save for a little later.
Based on lefty fails, I've come up with the list of supplies found here.