Im currently running at stage 1 and the standard GTI brakes have been great, no issues or felt I needed more. People usually tend to go for either standard brakes or bigger R32/S3/Cupra R brakes or if your names Hurdy then insane massive brakes that are bigger than my wheels.
If your not running crazy power id personally save the money, get standard brakes, they are pretty decent. If you still want to upgrade them then the easiest and best ones would be the R32/S3/Cupra R setup.