>>288128224-70mm f2.8 is the standard zoom to this kind of events, but you will be fine on the 24-35mm range for nightclub photography. Wider lens because you don't have much spare space in nightclubs or others parties, and you need to keep the group together to take the snap. A closer focus (15cm to 30cm) is another thing you must keep a mind on, exactly because of space.
You can aim for a 17mm if you want, or even a fisheye, it's your own style. I rather my prime 24mm because of light weight and possibility to make a better light painting when I have no space to shoot.
>>2881283 The flash light is way to strong than the ambient light when pointed direct to the subject. When it flash, it just froze the subject you focused on the first layer of your photo, so you're able to create any effect with your background. You need to learn how to properly use your speedlite for getting the better exposure on the first layer and let the background on the ambient and soft bounced light.
Sometimes it came out wrong when some lights get direct to your lens...
>pic related a fucking white light direct to my lens and eyes!