Assumption - You have a competitive product. You need a marketing/distribution support to get in front of the customers.
Medium to reach potential customers could be anything depending upon the target audience - Social media, Blog, Newsletter, Email, Web platforms like Indie Hackers or Starter story etc.
For the first 10,100d do it yourself within the 1-2nd degree connections and network; for 1000 should be founder and a sales guy/ BD guy networking eg at events and doing outreach via LinkedIn, for the 10000+ thwt when ide be putting money into a sales team or marketing resources
Obviously there’s wide variance for industry but I’d save if it’s B2C or “business saas” (like hubspot or canva) this would be reasonable to apply
How much I pay at 10-100 is just my time at 1000 would be 1 mid-level sales guys time at 10k+ would be based on my revenue and margins basically aiming to be ROI positive or at least have a return on CAC no more than 2