The lens you have covers the focal lengths that most folks consider for portraits. (80-135mm in full frame nomenclature).
For your camera divide by 1.6.
For portraits you generally want to isolate the subject from the background, so a wide aperture is desired.
The Canon EF 50mm f/1.8 would be an 80mm equivalent on your camera and the EF-S 60mm f/2.8 macro would be a 96mm equivalent. The EF 85mm f/1.8 would be a 135mm equivalent.
Set your lens to 50, 60 and 85 and see which framing you like best for your type of photography and pick the closest prime lens.