You should then test the ink supply by making a few marks on a scratch piece of paper. Be sure the ink flow is not too fast and not too slow. You can use black or coloured calligraphy ink, available from art supply stores or specialty catalogues, or gouache, which is opaque watercolour that many calligraphers use for coloured writing. There are lots of different manufacturers of these nibs, and you will want to try different kinds till you find the brand that works best for you. It all depends on whether you have a heavy hand or not.
Some nibs are more flexible, and some are stiff.
Stiff is better if you bear down pretty hard. There are so many different styles of calligraphy. Italic is the one that I started learning first. Each style is done with the pen nib held at a certain angle. Italic is done with the nib at a 45-degree angle.