Unless you are going to be doing mostly tank shots, I would go with a zoom lens instead of the 50mm. The 50 is a great lens and very sharp, but its very limited. My favorite afordable multipurpose lens is the 17-85mm 4-5.6 IS. That gives you an 27-136mm effective range. Nice decently sharp lens that is great for everything from landscapes to portraits. And although not a macro lens, you can zoom down to about a foot which isnt bad.
For dedicated macro lens, the 100mm macro seems to be the most popular, but the 60mm would do fine. If you want a closer macro shot, with 10MP, a bit of cropping wont hurt.