Prototyping in Axure can be rewarding because it allows for mocking up pretty complex systems. It's also really quick to figure out whether a certain direction makes sense or not with a smaller mockup.
This is a prototype of a site something like Craigslist, but with some additions and rethinks. While in a sales site like ebay you can see your previous sales, you have no way to compare them. Even someone who only sells 10-20 items per year could benefit from being able to see a better historical representation of where they have made their money. This could save time in the future on selling items that take too much effort, these could just be donated.
Another detail is the idea of "continuing on" instead of manually having to go add another item for sale. The user could either list another of what they're currently looking at, or start typing into the fields below the currently viewed item.
Illustrated in the sketch below at left is the idea of being able to see all of your items, both for sale and sold in the same location. Again, to compare with ebay, you often have to click back and forth between different sections to keep track of your items that need shipping, re-listing, or are just waiting for a buyer.
In the 2nd image, I was thinking through how a continuously scrolling interface might work that also allowed you to get details of the items you're scrolling by.
Another step was the creation of information architecture documents. I'll often start out in something like OmniGraffle, but in this one I finished it using Axure.
Last is a sketch for a social site. I was figuring out which elements would go or fit on each page.
I've created prototypes using many methods. Sketch, paper, objects/models, Axure, UXPin, Sketch, InVision, Proto.io, Marvel, Adobe XD, Keynote, and more. Each has their pros and cons.