Nikon D5300, flashgun for night/club photography?

I'm a photography student and I'm needing to buy a flash gun that is appropriate for this kind of work. I've only ever used flash guns for portraits and stuff in light conditions. Any help would be great… My max price would be about £300

SB400.

You aren't going to get a Quantum T5 for that money, so look off-brand like Metz or Sigma. The Sigma 630 DG Super has plenty of power (right up there with the SB-900) full i-TTL support (just make sure you get the Nikon version) and should be well within your budget, so you can get 8-12 rechargeable batteries and a good charger for them. The Metz 58 is also a very good choice, but the price may be above your budget. Nissin is coming along nicely as a good flash as well, again the top of the line may be over your budget.

The SB-400 is inexpensive for a Nikon flash, but also woefully underpowered for club work. You need all the power you can afford. Flash power is one of those things where you can't have too much, but you will notice too little very quickly.

Then you will need to practice with the flash, and learn the quirks of any TTL flash system. You will find that certain scenes will cause a TTL system to overpower the flash, and certain other scenes will do just the opposite. It is better to understand what the flash will do before you attempt to use it in a "real world" setting.

Another option is something like a Metz 45 handle mount. You need a PC socket to use one, other than that it is an amazing piece of gear. It is an auto thyristor flash or you can shoot full manual, but you also have to have the camera in manual mode to use one. An auto flash is more consistent that TTL in most situations, but also easily adjusted for those scenes that want to fool it.

Even a Yongnuo 560 in manual mode is very useful, if you take the time to learn how to use it. And with your budget, you can buy 4 or 5 of them for some really creative lighting.

That is a Metz 45 in the avatar… I have 2 of them, with radio triggers so I can put them on light stands, or keep one on the camera for more mobile work. I used to shoot weddings with them, I don't do weddings any more, but I didn't get rid of any of the gear.