Lens advice for a beginner photographer?

I'm pretty new to the photography thing and I know very little, if anything, about lenses. I've had my Nikon D90 for about a year and, after a whole lotta saving, I'm starting to look at possible new lenses.
My cousin, who was a professional property photographer and also photographs in his spare time, swears Tamron is the best for your money's worth. He also says that Sigma, from his experience, is a very delicate brand? Easily breaking n' all.

I'd like to get a Macro, and I think I've decided on the Tamron 90mm, but after reading up some reviews that says it's a very slow lens, though I prefer the shots that come out to the sigma shots. I figured I'd do some field research and ask some photographers themselves (you)(hoping that someone out there owns ones of these) and see what people had to say.
Exactly how slow is the lens and does it get in the way of shoots?

I would also like a wide-angle lens, I've been comparing the Tamron 10-24mm and the Sigma 10-20mm, and I seem to be leaning toward the Sigma, for several reasons, but I'm wary because of what I've been told about how delicate the lenses are (obviously, I wouldn't be rough handling them or anything, but accidents are unfortunate and sometimes I'm an accident magnet) and I'd love to hear some opinions from some people who know what they're talking about.

These are all very diffrent lenses; skateboards to bulldozers. They all do their job well, but a diffrent job, each one.

Slow means a small minimum aperture. You can only use a 30th shutter speed with a slow lens when a faster one will let you do a 125th, so less chance of blurry pictures. Decide what job you can't do with the lens you have now and hopefully it's a job you would like to do in the future.

If you want to do macro get a macro lens. If you want to do wide shots get a wide lens.

Stay OEM and never look back.

The Nikon 10-24mm AF-S Nikkor f/3.5-4.5G DX ED and AF-S VR Micro-NIKKOR 105mm f/2.8G IF-ED are two lenses you might want to study.

Interesting that you mention the Tamron 90mm Macro. It's the only third party lens I have ever considered getting. At f/2.8 it's fast enough and the sample images I have seen are wonderful. Reviewers have mentioned that it is fragile. You don't want to bang or drop it. Of course, that is true of any lens. At $409.95 the Tamron SP 90mm f/2.8 Di may not be a bad value.

The only generic wide angle zoom I can recommend is the Tokina 12-24 mm if you can't budget for the Nikkor 10-24 mm.

The macro lens you will find most valuable is the Nikkor 60 mm f/2.8

I don't know how much experience your cousin has as a professional photographer, but if you just look on the sidelines at various sporting events, you will see that All of them that shoot with Nikon's use Nikkor lenses. For good reason. They last for decades.

Since I shoot a lot of sports, I sometimes get run over by athletes as they crash out of bounds and into photographers, players, coaches and game officials.

Nice camera by the way.

Sigma's more expensive line isn't especially delicate. I would also look at the 10-20.

All 3rd party macro lenses are optically solid. All are slow to focus when they have to go from infinity to closest which is why they have limiters. The tamron 90 and the tokina 100mm feature an AF/MF clutch which means that you can switch to manual focus by simply pulling the focus ring, handy if you want to override AF without taking your eyes of your subject.
Personally I like Tokina. Despite what photozone writes about CA I like their products. I own the100mm macro which beats the tamron 90mm when it comes to build quality.

I've also had the chance to test their 11-16 and 10-17 and 12-24 and Like the first and last, t he fisheye look of the 10-17 is not my thing.

The highest rated wide-angle was the Tamron 11 to 16mm F2.8.

I have both those tamron lenses and am VERY impressed with them…

the macro lens might be slow, but that isn't a problem, as i shoot inanimate objects…