Photography gear buy/sell

I used to do nightclub work with a Canon 40D + 17-40 L USM. Went through a few flashes trying to get something weak enough and small enough to light the foreground only and not get knocked off the shoe by drunk people.

You want a really wide lens. If you struggle finding one wide and cheap enough, use a 0.4x or 0.7x adapter if the lens is strong enough - only use on internal focusing lenses, not ones where the front part moves in and out and rotates.

Just buy the cheapest widest lens in your budget - it all looks the same after you process the images to look like the horrid nightclub aesthetic.

I’ve shot around f4 -f8 at parties and in clubs using manual focus. If using an slr I recommend a flash bracket like the Custom Brackets CB Mini-RC. It makes the whole setup with a full size flashgun easier to handle and puts the light source very close to the lens, like a compact camera (and not dissimilar to a ring flash).

edit: or that ^ might be too slow, any advice?

It obviously depends on the lighting situation, the ISO capabilities of your camera, your decision on what is acceptable image quality..
..and what kind of photos you are actually shooting - people dancing? People standing around and looking cool? Artists on stage?
If you want to get sharp shots of moving people (including yourself - if you're in a crowd) then f4 might not cut it. On the other hand if your camera can handle high ISO very well then it works.
Of course with flash you'll have enough light, but, to state the obvious, EVERYBODY will know you are taking photos of them, which, you know, changes everything.