Um - you haven't. It's obvious. A search for GTA would bring you many threads. That might even lead you onto Safedisk 2.51 which there's even more of - with step by step guides.
Also you haven't stated what your burner is which makes everything more difficult of course.
So download
Clony XXL, make sure you have the latest Clone CD (version 4).
Yes you can still copy the game with just one drive - it can be copied to the hard drive in an image file first then burnt back to CD-R.
It's very likely that your drive won't be able to copy SD 2.51 so give AWS in Clone CD a try (Clony will tell you this anyway and set it up for you)
As you've only one drive, you'll be playing the copy in it so enable Hide CD-R Media when you play it to disguise the ATIP check.
And also, why would cloning the game make it run better??!!!