Gerund/Gerund Phrase

That is not a gerund, it is a present participle phrase. In a gerund phrase the gerund is always at the start of the phrase.

A gerund phrase consists of a gerund, its object, and all modifiers. For example:

Eating blackberries without washing them will make you ill.

In the gerund phrase above:

Eating is the gerund.
(A gerund phrase always starts with the gerund.)
The word blackberries is the object of the gerund.
(The object of a gerund is also called the gerund complement.)
The phrase without washing them is a modifier.
(In this case, the modifier is an adverbial phrase.)

Doesn't a present participle phrase only function as an adjective? In this sentence, "Much gesturing" seems to be treated as a subject.