Your mission is to fish all you have is a rod, a rowboat, and the ocean. What are you going to do? This is the analogy of what business owners face when dealing with thousands of skus of varying manufacturers they represent. Manufacturer Catalogs are the categories of bait, the skus represent the specific bait within each category. The first thing you have to know is what kind of fish you are fishing for aka consumer. The second thing you have to know is which category of bait you are going to use. The third thing you have to know is out of the bait categories which specific pieces aka skus are you going to use to bring in the fish you want.
What I just described is catalog and data management which are underappreciated art forms and skills. If you are an eCommerce proprietor you are going to have catalog feeds galore if you are building an all-encompassing site. That data is going to be difficult to segment, market, and merchandise in a palatable way for your consumers. You also have to think about your consumers which categories and specific skus are going to resonate so you can be profitable. Some skus sell immediately and are transactional while others are one-off buys or languish until there is a specific need once a year or longer. You need to address both factions of products because you need a happy balance. There is a need to segment your audience and the products they interact with. There is also a need to have a manageable level of catalogs and feeds so you can be agile and efficient in dissemination of information on your website. There is also a need to properly monetize and merchandise your skus and products so they are accessible for your audience. You also need analytics to measure your consumers and their behaviors toward your products and categories.
Most companies get the catalog feeds direct from the manufacturers or hire a catalog provider to supply the feeds either way you are going to have lots of data to deal with (some clean and some not). Its your job to do the segment and merchandise work or you can pay someone to alleviate that burden if you have the means. Either way, you are looking at a monetary and time expenditure to launch and manage properly.
In the end, we all start off with a rod, a rowboat and the ocean. We need to eat on the transactional business or small fish before we can feast and get fat and happy feasting on whale. Starting out, we need enough small fish to get us fed and to sell overstock to upgrade to nets, a larger fishing vessel, and harpoons. This transition is a process, and takes time and that is why it is important to think about what we can immediately do with the catalogs and data we have now, so we can make those upgrades and start hunting whale.