Much like what Ronnie said, you'll want to narrow your niche down to a specific line of products to keep your business plan focused.
A great way to figure out what products you can sell is by using Google Shopping Insights. This tool allows you to see what products are currently trending, and what products are upcoming. This tool is useful as it will allow you to forecast the hottest product - imagine getting in on the fidget spinner craze before it happened - That's essentially what this tool can help do!
Best of luck with getting the new products added up! Feel free to shoot a response here when you're done and I'd be happy to take another look!
Have a great weekend!
All the best,