Do you have an eCommerce website?
Or, are you going to start a new eCommerce website?
Making a marketing strategy is a must for your eCommerce website. So what are you going to sell? Who are your target customers?
You are not going to sell everything on your site, I think. So be specific and define your niche.
Then you need to do the market research and try to understand your customers. You can offer something that is unique and solve their problem.
When anyone visits your website, make sure she or he has a good user experience. You need to do SEO on your eCommerce website. You should not keep specific products more than 3 clicks away.