Gestures are treacherous precisely because they feel universal and are not. The classics that flip meaning across borders: the thumbs up is positive in most of the West but offensive in parts of the Middle East and West Africa; the OK finger circle is fine in some countries, vulgar in parts of South America and Europe; and a palm-out hand can read as an insult in Greece. Beckoning someone with an upturned curled finger is how you call a dog, not a person, in much of Asia, where the polite version is a palm-down wave.
Body positioning matters too. In many Asian and Middle Eastern cultures, showing the soles of your feet or pointing them at people or sacred images is disrespectful, touching anyone's head is off-limits in Buddhist cultures, and pointing at people with a single finger is rude nearly everywhere, so use an open hand instead. The left hand should not be used for eating, greeting, or handing things over in many Muslim and Hindu contexts.
Safest defaults everywhere: keep gestures small and hands visible, mirror local body language, and look up gesture taboos for your specific destination before arrival.