CMcGrath16: I am not really an advocate of nice glass in nightclubs. It, actually depends, on the look you are trying to achieve.
You will more likely notice an improvement in your images in a better body than better glass.
I use a 5DMKII. You know what glass I am using now? This rubbish 35-70mm lens. I think it was manufactured 10 years ago or so. It cost me 30$.
I used a 16-35L 2.8. before this, and while great, it was heavy, and not really worth it financially to lug it around a nightclub environment.
If you look at my images, you can't tell the difference between the two lenses.
It goes back to your settings that you shoot at. I shoot at iso100 most of the time, f4.5. Sometimes Ill boost the iso to 1600/2800, but still keep the fstop at 4.5. I don't really "need" the extra fstops that 1.8, or 2.8 provide.
On the other hand though, you buy cheap, you buy twice. Good glass is great when you decide to print the images, or studio settings. I think that a majority of nightclub photos dont reach beyond the web.
For me, it's not worth it. But I am sure other photographers might disagree.
If you check out the site: ambrel.net, the images were shot with a Canon 5D and some horrifying lens. I think it was a 28-120 kit lens, or something similar. Cheap glass. But the images come out beautiful.