I would a website that looks fresh and modern.
The main website should include, Premium Listing of products, a small newsfeed, categories, the latest products listed by users. When clicking on a category for example â€˜â€™Computersâ€™â€™ you get once again the Premium listing for that category (admin control of the listing), then the list of all the other listings in the category that could be organize by date or price, then filters that filter the action such as Buying, Selling, Currency, Location.
Now user side, when I try to publish a product I should be given the opportunity to Select a category, Title, location, action (buying or selling), price and currency, text box with Details, embedded video capability, images to be uploaded. Then if the category has a sub category for example â€˜â€™Computersâ€™â€™ and subcat â€˜â€™laptopsâ€™â€™ I should be able to put the specification of the laptops in separate text boxes that will organize the information accordingly like CPU, RAM, MODEL etc.