I would suggest changing up the way you are outlining things. The problem with pens is the lack of control over the line weight, and having a degree of control over that really helps pieces like this (I would recommend using a brush, but that is another skill set with another learning curve). When the color changes from dark to light within a leaf, you want to be able to show that change with just dots, rather than with a line (unless you don't have a choice). Additionally, make a stab at attending to details like the points on the edges of some of the leaves with the initial lines, rather than going back and adding them on to the outside in black (which creates an effect like the leaf is wearing mascara). Drawing the little fuzzy plants in the background, or even just doing the background as a uniform darker color (rather than the lighter color) would also help the plant to stand out.
Also what kind of critic would I be without pointing out bullshit semantical details: this is stippling, pointillism applies to colored things.
edit: oh snap I just read the original post again and realized you were looking for materials suggestions not art suggestions. I will leave the above stuff up, maybe it will be helpful, take it or leave it. As for pens, I can't stand microns, but I've yet to find a better alternative. Again I would suggest picking up a small brush for the outlines, but that is your call (if you DO want to go the brush route, I would suggest sumi ink over india).
As for paper, you can't go wrong with bristol board.
