A great classical text is now online:
Quintilian: Institutio Oratoria
It is a massive work of twelve books used to educate boys to become orator. Part of becoming a good speaker is mastering the delivery of your message, through appropriate use of voice and gesture. This is the topic of section 3, Book XI. (lines 1-2, 14-15, 61-149 especially).
Quintillian came from Spain but taught in Rome in the first century AD. His very influential work builds on that of Cicero, who discussed gesture in oratory as something to be cultivated, and before that Aristotle, who discouraged gesture and other theatrical means as mainly working on the emotions of the public, favoring pure reason instead. Quintillian separates what is appropriate for orators and for actors though. For orators he gives some very specific guidelines on gestures, how to make them, and when to make them.
So, do you want to be seen as a captivating presenter, a convincing lawyer, or a trustworthy politician? You will have plenty to learn from Quintillian. Somehow, I don’t think the instructors of our days such as Lenny Laskowski, these guys, this guy, or any of these for that matter have much better to say.