You'll first need to define what side of YOUR marketplace is demand and which side is supply. For example, for DonorsChoose.org, I define the teacher need as "demand" and our donors' donations as "supply". In our case, we needed to have enough demand (teacher projects) before we started advertising such need to our donors. However, once we had enough demand (i.e. choice for our donors) it then became difficult to find the "supply" to meet that need, so we had to re-assign our resources from finding more teachers to finding more donors. You'll find that you'll always have an imbalance in your marketplace and you'll need to have enough demand and supply for the marketplace to thrive. You'll need to shift your resources from "demand outreach" to "supply outreach" (and viceversa) based on how your marketplace is behaving.