using

[wowenglish1]

I wonder if "using" is gerund or participle.
You can save much money using coupons.

[Ilki]

You can save much money [(by) using coupons].
You can save much money [thus].

"(T)hus" is an answer to "How?". "How?" triggers the adverbial interpretation. Be careful not to be hasty in judging things, however. Trickery is involved here! There is an elided preposition "by" in the sentence whose complement is the -ing clause, the status of which engages our interest. Prepositional complements are nominal in nature. Gerunds are nominal -ing forms. By now it should be painfully obvious to everyone that we have a gerund-clause here.

[5jj]

You can save much money [(by) using coupons]......You can save much money [thus].

"(T)hus" is an answer to "How?". "How?" triggers the adverbial interpretation. Be careful not to be hasty in judging things, however. Trickery is involved here! There is an elided preposition "by" in the sentence whose complement is the -ing clause, the status of which engages our interest. Prepositional complements are nominal in nature. Gerunds are nominal -ing forms. By now it should be painfully obvious to everyone that we have a gerund-clause here.

That's one possible reading. You could also think of it as a participle in a different elision: You can save money (when/while you are) using coupons.

This leads to two points.

1. Talking of elision is always potentially dangerous. When we have only the words uttered/written, we cannot be sure that there is an elision, or, if there is, we cannot be sure exactly what has been left out - because it's not there!

2. Labelling is not always helpful. It is clear that we have an -ing form in that sentence (i.e. that part of the verb that ends in -ing). Does it really matter what label we attach to it?

I don't think the word 'trickery'is very helpful here.

[Ilki]

Does it really matter what label we attach to it?

As long as we do know what task a string of words perform, what meaning they carry, no.
Labelling is short and sweet. It has its virtues, nonetheless.

[Ilki]

I don't think the word 'trickery'is very helpful here.

The OPs question is trickier than meets the eye.