Hey buddy, welcome to golfgti.co.uk
Advice on track car - have a poke around in the motorsport section, there have been a few threads in there.
However, in short, the recipe is:
Loose un-necessary weight (back seats, carpet, sound deadening etc) - How far you go is determined by how usable the car needs to be on a day-to-day basis. Not only will this make you faster (improved power to weight) but it will make your standard suspension and brakes operate better (not hauling down excess weight from speed) and will make your car less expensive on tyres and brakes during track time.
Sort brakes - Better brakes will allow you to arrive at bends faster, and brake later and harder. Better set-ups will allow more track time before they fade also. The track is a great pace to highlight how awful standard cars actually are!
Sort suspension - Similar to brakes, better suspension will allow you to carry more speed through the bends.
Up your power - give you some more squirt in between the twisties.
Just make sure you and your car are safe. Invest in decent helmet, fire extiguisher, consider a decent seat/harness setup. Make sure your car is in good order and set for the track before you go anywhere near it.
