If you have a finite number of products that will allow on an order (for example, they can only order up to 10 items) then you could use an individual section for each product, and use conditional logic (based on the answer to a question “do you have another product”) to shown them as necessary. Each section would have fields to collect all the information you need about that product.
In order to repeat sections of fields, you can use this add-on for Gravity Forms:
Or, there is this 3rd party solution which may be exactly what you are looking for: