Hi Harriet, welcome to the forums!
Before you go, crank up the ISO to whatever the highest setting is and take some photos around the house. Check to see if the noise generated is "acceptable" to you. You're looking for ISO 6400 or higher if it'll go that high.
My "go to" gig settings are 1/60 sec, f/1.8, ISO 1600 maybe 3200. This is a ballpark figure for film which doesn't mind being under-exposed a little and has quite a bit of latitude. Digital may give different results.
A min aperture of f/4.5 is roughly 3 stops away from f/1.8 so I would "guess" that somewhere around 1/60, f/4.5, ISO 6400 might get you in the ballpark. The problem with the kit lens is that IIRC the min aperture changes as you zoom, and 4.5 will be at the 18mm end. If you try to zoom in on the action you may find the minimum aperture suddenly becomes 5.6 or 6.3 or something like that which is yet another stop less light.
1/60 sec is about the minimum I'd expect to get reasonable results. Ideally I'd want to use 1/125.
My suggestion would be to set the camera to Manual. Set the aperture to the minimum, set the ISO to the highest, and set the shutter speed to 1/60. When you're in the gig, take a random shot and look to see how it looks. If it's too dark, you could try 1/30 sec to see how that looks. If it's over exposed, I'd got to 1/125, then if it's still over, start pulling back the ISO. Using Auto modes can be unreliable because the lighting is usually all over the place and the camera meter gets confused. Also your flash will keep popping up which is often a no-no at gigs.
It does depend quite a bit on the lighting and type of gig. A pub thing that has house lights on for an acoustic guitarist and plenty of space for you to sit without being jostled will be completely different (and much easier) to something with flashing lights, house lights off, and people bumping into you left right & centre whilst hurling beer.
Also, if it's very dark, the auto-focus will hunt for the subject and may not find it, resulting in you pressing the shutter and nothing happening. Might also be worth having a practise with manual focus before you go so that you have a bit more control.
If you find you enjoy it, the 50mm f/1.8 lens is very reasonably priced and will give you f/1.8 which will make things much much easier to get decent sharp images with acceptable noise control.
Enjoy the gig, and good luck!
