Hey guys

I am new to this so I hope I do not post in the wrong area etc!

I have a yellow astra J gtc sri - its a wonderful thing, quite nippy and it stands out. However being me, I want it to sound good.. Can someone please suggest what would be the easiest and cheapest way to do this for my gtc? I am not an exhaust expert and I not a dummy too lol (I wont drill a hole in my exhaust or any of that silly stuff)

So it would be great if someone could advise me with this