Currently, there is no way to deploy the data required to have multiple currencies in your target org.

You can deploy the settings for enabling multi-currency using the Settings metadata filter (select Currency within Settings for more specificity if required).

Once this is deployed, the target org will now have multi-currencies enabled. However, the actual currencies are data rather than metadata, so those will not be included. And unfortunately, Gearset does not currently have a way to deploy this data.
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This is expected behavior. The IsoCode field is a create-only field and right now we don’t support deployment of those types of fields for primary objects in data deployment.

Below article contains further information on what Gearset can support:
​Which objects and fields can be deployed using Gearset's data loader?