The ink discussion can often be a subjective and broad topic with lots of personal opinions and choices - which is actually part of the fun of using fountain pens .  My advice is to experiment with as many types as you can to find what you like, but be sure to only use ink designed specifically for fountain pens.  India ink and calligraphy ink can cause permanent damage to the nib, feed and reservoir of your fountain pen.  So be sure you buy the right type of ink.