If you were the owner of a new shopping mall and did not have any stores rented out before you opened, it would be a hard sell to get those stores filled afterwards, as all people would see is a big empty mall. The same goes for an online marketplace.
My strategy is to fill it with a high number of low-volume products from my own store, thus giving it the appearance of a busy marketplace, until such time as I get more tenants.
I've already made a small profit on the marketplace with a very small number of products. But I need to create more products, so I've been doing research on one of the highest selling items in my market: vehicle decals. I researched high-volume professional vinyl cutters vs low-volume home/small business ones. I have determined that with the purchase of a home/small-business cutter along with the other necessary tools and supplies, I can design, create and sell an appropriate number of decals.
I am ready to purchase and will be making room in my home office for this equipment, setting it up, getting used to the equipment, and then designing some decals to add to the marketplace. I can manage some of the design myself, while outsourcing to a friend of mine who is a design professional. These will be JIT (just-in-time manufacturing) goods. I give myself the goal of end of August to begin adding new ready-made decals to the marketplace.