I judged a Speech Festival a couple of years ago and was stunned by one of the candidate's performances. Not by their brilliance but by their ressemblance to a windmill. The boy in question was reading a serious, calm poem but had matched it with exuberant, dramatic gestures.
Gestures will not win you a Speech Festival. At best they are unnecessary and at worst they are a distraction. Focus on the face and the voice and avoid oscillating wildly and you are in with a chance!