I am using a sigma F1.4 lens without image stabiliser. I will normally experience slightly blur image due to camera shake. Maybe 100D body is too light...hahahaha. I try to take at shutter speed above 1/160 to prevent that.
To solve the problem, it probably gives me an excuse to buy a better camera which supports higher ISO. LOL
To me, if you still have the kit lens that came with your 100D. Try shooting with the 18-55mm lens first, at least it got
IS which will help. What you should consider investing would be a lens with IS and tripod instead of a newer camera.