B2C marketplace in learning - How do I get my first users? - I will not promote

Early-stage founder here (2-person team, not sharing the name since this isn't a promo post). Where we are: The supply side is working. We have about 10 users signed up. We had a waitlist of 25.. I'm getting the remaining signed up/onboarded on the real platform now. Most of this has been through 1-1 DMs. Getting reach with demand has been hard. I'm building a social presence, but my following is still small. I keep seeing founders here with hundreds of free users within weeks, and I'm curious what's behind that. Was it one channel? A launch? The right community? Specific questions: If you got your first 100 users without an audience, what actually worked? For marketplaces: did you grow one side first or both together? How do you approach communities or partnerships at such an early stage without coming off as spam?