Well these days you could spend £500 and get a wicked setup, all clothing etc and you would be tournie worthy (your skill is up to you
)
But on the other hand, you can spend well over £1000 on a gun if you wanted. Thing is, in a tournament, all guns are locked into the same mode, and do the same thing, so it is not vital that your gun is purple and lime and can text your snake guy using bluetooth, but you also have that choice "if" you have the money.
Are you thinking brand new or second hand? If you post up what you think, we can maybe steer you in the right direction. Be aware that you will get offers of guns in any thread like this. Just don't take the first thing that comes your way, and do a little research before you commit. If you need, PM me, Lump, Gassy or Impulse Raider and you will get impartial advice and plenty of it. Or make a thread and see what people say.