Here are the easy to track, and most important metrics that should form your first KPIs. They are relatively easy to track and will provide a great foundation as you grow and add more detailed metrics.Unique Visitors
Growth unique visitors is a proxy for being found, being viewed and your reach. You can use simple tools like Google Analytics to get accurate data.
These are also called "subscribers". This is the so-called "follow me home" metric. This includes everyone who starts to follow you. This includes people who give you their email as a newsletter subscription, or who follow your RSS feed, podcast or Video Channel.
Not the same as "contacts" or email addresses. When you get started it's sufficient to define these as "hand-raisers". Hand raisers are people who have shown interest in an actual outreach by your team. Examples are people who have filled out an explicit "Contact me" form, or a product demo request. So subscribers to your newsletter or people who signed up to get a free gift don't count as leads.
When you get bigger you should start differentiating as follows:
Try to measure conversions through the funnel as granular as possible, as long as your data is accurate and meaningful. Here is a typical prioritized list of conversions to measure as your dashboard gets more granular
With these metrics on your dashboard, you can manage your marketing function responsibly.