Calling all Wordpress experts

I've created a Wordpress site for my business but am having trouble getting the theme I've purchased to do what I want. I've been in contact with the designer and have been assured it's capable of doing all of the things I want, with exception to the user form, which will need to be built. The site will be a community marketplace like Gumtree (see [login to view URL]), allowing users to login and post their own items. The theme chosen ([login to view URL]) allows the layout to be like Pinterest - gallery style, woocommerce has been installed, and I want advertiser plugins. There are a few things I'm having trouble with: • I want non-members to be able to see everything, but not able to add items for sale or respond to sellers • I'm not sure how to set up the system so users can request membership to the site • All posts will be added by other users and then approved by me (the administrator) • I want the site to look like the Pinterest layout option - [login to view URL] (but also allow users to change the view to suit them) • I want a really simple form for users that lets users (just like Gumtree): 1. Set the item price (in AUD) 2. Give their post a title and description 3. Choose categories the item is posted under 4. Add pictures, embed video 5. Add contact details 6. Add map address 7. Share their ad (once approved by admin) on Facebook, Twitter, Pinterest, Google+, via email etc 8. Choose to pay an additional fee (to me) to bump up their ad, make their ad a featured ad, urgent sale etc (again like Gumtree) Functionally the site should work much the same as Gumtree, but visually be much simpler (which is why I've chosen to use WordPress and a theme). There doesn't need to be a shopping cart facility, as all transactions will occur elsewhere, but pricing, location etc needs to be visible. Thanks, looking forward to your responses! Alissa