I think Alessandro has read the question wrong. An angel investor rarely invests in a plan. They invest in the entrepreneur and any evidence that the entrepreneur is on the right path. This is ideally expressed in some form of early traction, or at least early external validation.

Early validation in your case would show that you've already run customer acquisition experiments and proven a stabilized CAC. And that you've run some basic experiments to show that acquired users are willing to transact in some way.

In other words, a plan is likely not enough to convince investors to invest.