You need customers who PAY and STAY.
Getting to MVP (Minimal Viable Product") is an important milestone. But you’re not ready to invest in marketing unless you get to Product Market Fit. You need to know what a good customer looks like before you can try to find more of them, let alone pour fuel onto the fire.
Reaching PMF can be measured by many factors. The easiest is to count the total amount of revenue that is generated by multiple customers (I’d say at least 5-10) and adds up to $1M in Annual Recurring Revenue. These are basically customers who have paid you, and stay beyond their initial annual subscription commitment.
Until you reach this point, you need to be on your guard before you commit to a certain vertical, segment, Go-To-Market or business model, as you really don’t know if your customers are still mostly made up of Early Adopters who happened to just like what you’re doing.