Well, where shall i start.
What camera do you have now?
What other equipment do you have?
Are you going to become a professional photographer?
What are your budget limitations? You say price does not matter, but lets be honest, it does.
For arguments sake, lets offer you some kit.
Camera - A Nikon D3s for example. Incredible in low light.
Then you'll need some lenses. Indoor party, hmmm, a general purpose 24-70mm f2.8, a portrait 85mm f1.4, and some more zoom with a 70-200mm f2.8. Sound good?
You'll definitely need at least one flash - SB900 should do the trick.
So let's total you up shall we. This is based on rough prices, but you're looking just over £9,000, and that's without any real lighting setup, a tripod or any other accessories.