This is up to you, however we recommend you do a niche store and here are the reasons why.
- You can sell a variety of products in your niche
- If your first product does not work, you don’t need to make a brand new website
Note: If you do a single product store and it doesn't work, then you may need to make another website, with new images, new content, new domain name, new logo etc. this can become costly in both your time and money.
Try to avoid making a general store.