You seem to believe your inventory size and search function are your bottlenecks. They aren’t. You need marketing help, and I don’t mean SEO or “online markting” help; actual marketing help. Do you have a marketing plan? (Hopefully at least a business plan). Who are your customers? Market size? Where do they hang out? Most importantly, what do they need/want that you are the prime provider of, that they can’t get anywhere else? What’s your value proposition?