Before product-market fit, complexity is your enemy. You need to know three things: Are users signing up? Are they activating? Are they coming back? Everything else is noise.
Activation and Retention. If users aren't finding value (activation) or coming back (retention), nothing else matters. TenScore weights these at 40% combined for exactly this reason.
As soon as you have users. Even 10 users can tell you if your activation flow is broken. Don't wait for scale to start measuring health.
Your activation event is the moment a user realizes value. For a project management tool, it might be "created first project". For a CRM, "added first contact". Pick the action that correlates with retention.