TL;DR: I built a product in a niche space that I worked in for 15 years. The product works, and I got initial conversions, and the market is also proven by a few bootstrapped competitors. The issue is that distribution is entirely based on PPC, and I'm bleeding cash trying to train the bidding algorithm on a small budget competing against other competitors with deep pockets.

How do founders raise money specifically for ad ramp-up when the "moat" is basically marketing execution and capital?