Hi- If you don't intend to use a big telephoto lens on the tripod as well, you could opt for a smaller, lighter one. For macro photography I would consider one with a central post that you can adjust up and down, and reverse to get down low. There are a lot of cheap and pretty nasty tripods out there so if you want quality I would stick with Manfrotto, Gitzo, Feisol et al. That covers the legs but you have to think about a head too. For macro work a ball head works very well. There are several good brands out there. Again, if you don't need to mount anything heavy, then a light-duty ball-head would work fine. Manfrotto, Gitzo, Giotto, Really Right Stuff, Kirk, are names to look for. Finally you have to think about how to attach the camera/lens to the tripod head. The industry standard these days is Arca-Swiss so you would need an Arca-Swiss lens plate to attach to the bottom of the camera, or a plate to go on the tripod ring for the 100/2.8 if you have one. If you go Arca-Swiss make sure the head has an Arca-Swiss clamp or can be adapted. I really don't like the Manfrotto plates which fit nothing else and come in at least two varieties.