Start with the buyer
Start with who your store is for, not with what pays best. A buyer who trusts your taste comes back. One who found a random list doesn't.
Check what happens after the sale
Pick products you'd recommend to a friend, then look at the seller's shipping times and return policy. Your name is on the page, even when someone else ships.
If you can, order one yourself first. Nothing teaches you more about a product than unboxing it.
Keep the range small
Keep the range small at first. Remove what doesn't sell and add what buyers ask for. A shorter list is easier to browse and easier to trust.
Use a simple test
Before you add a product, ask three things. Would I buy this? Would I be happy to answer a question about it? Does it sit well beside what's already here? Two yeses aren't enough.
Keep a short list of products you've turned down and why. It becomes a clear picture of what your store stands for.
Mix in a range of prices
Give buyers an easy first purchase and something to save up for. A store with one low-priced item and a few considered ones feels more complete than a page of similar prices.