I guess you're looking for a shopping cart plugin? There are plenty, but I have to say..WordPress is such a pain.
I don't know if pricing would be worth it to you, but it will save a ton of time and aggravation...try Shopify or Squarespace or something similar where all you have to do is plug in a title, description and price. Your life will be much simpler.
If you don't want to pay the monthly fees, I believe WooCommerce is the plugin you're looking for.