I have a Lamy as well, but find the nib a little more scratchy than the kit nib that came with my Berea roundtop fountain pen, although I do use my Lamy alongside my Berea roundtop on a daily basis. That aside, I agree with others that a converter is a much better way to go than cartridges. The Lamy converter will run you about $5, and is worth the extra investment.
To learn more about different inks and see color reviews, I'd suggest looking at the
Fountain Pen Network forum, and look under "
Inky Thoughts" and "
Ink Reviews" for more information that you can absorb in one sitting! Another great place for ink and pen reviews is from the "
Spiritual Evolution of the Bean" blog, many of which you will find also posted at the Fountain Pen Network.
A couple of vendors also provide ink samples for purchase that makes it a little easier to find the color and brand you like.
Pear Tree Pens and
The Goulet Pen Co. both offer these ink samples. Brian Goulet of Goulet Pens
is also an IAP Member (IAP screen name "
GouletPens"), and has a blog called "
Ink Nouveau" that also offers ink reviews, etc. I've ordered from both Pear Tree Pens and Goulet Pens, have had excellent service, and would order from both again.
edit: Pear Tree Pens also offers the Lamy Converter:
http://www.peartreepens.com/Lamy-Converter-Z24-p/lz24.htm