When using influencer marketing to promote your brand or product, a few key return on investment (ROI) metrics you should focus on include:

1. Engagement Rate: This metric tells you how much interaction an influencer’s posts are generating. Higher engagement rates typically indicate a more engaged/invested audience, which can lead to higher conversion rates for your campaign.

2. Reach and Impressions: ‘Reach’ represents the number of unique users who saw your content, while ‘impressions’ shows how many times the content was displayed, regardless of clicks. These metrics can give you an idea of the broad visibility of your campaign.

3. Conversion Rate: The definitive metric for many campaigns, tracking how many users moved from viewing the influenced content to making a purchase or completing a desired action.

4. New Followers or Subscribers: The influx of followers or subscribers after the influencer’s promotion can be an encouraging sign of a developing customer base.

5. Cost-per-engagement or Cost-per-click: These metrics show the monetary cost for every interaction or click achieved by the influencer’s content, key in understanding campaign value and efficiency.

These metrics offer a wide view of your campaign’s effectiveness. Using platforms like Flinque can help you track them and manage your campaign more effectively. Keep in mind that different platforms might offer different ways of tracking and measuring these metrics, and the best for you will depend on the specific needs of your brand and campaign.

Remember that each campaign is unique and what works best for one may not work as well for another, so it is crucial to set specific goals and select the most appropriate metrics to focus on for each campaign you run.