Very cool! You still managed to get a lot of detail out of the photos, especially the first photo!
The first lens you should get now is a 50mm. Its the cheapest lens Nikon offers and works perfectly with either the reverse ring, or macro stacking filters. Both of these work well (and are really cheap). I got the stacking filters to be able to control how close you get - with the reverse filter you can't. That's essentially the poor man's macro solution. I also cant afford that 105mm, although I would LOVE that lens :D