Build an Online marketplace + wish list -- 2

I want to create a portal + an app for iOS and Android systems that will be like a marketplace (Amazon, eBay, etc.) where we'll have 3 kind of users and different features: All features should be available from web and from mobile apps - RETAILERS: They can open a shop into the portal and/or list the products they have to sell. The shop will have all the same features they have on eBay including instant messaging with customers, options like bold text, colored background, list on the top, etc. Retailers can list for free their items, options will be paid and also they will pay a % per each sale they make. They can put objects for sale just as they can on the most popular portals with same options and features. - CUSTOMERS: Customers can make their own big wishlist and specify if it is for: birthday, nameday, anniversary, marriage, graduate, etc. and they can share via social media and email with their contacts that will be invited to see the wish list and buy a gift. When a friend buys a gift the customer will get an email and can have the possibility to send a thank you message from our website. Both invitation messages and thank you messages can be customizable by customer. It should be very easy to share the wishlist on main social and also via email (the system can be allowed to enter the mail box and collect email address automatically and/or manually and also the customer before sending can control the list and add/remove some addresses). When a customer makes his own wish list he can decide if his friends can pay only the whole price or buy a part of the product (read below for details) - FRIENDS: Friends will have the possibility to check wish lists of their contacts going trough a search engine or just because they got a message from the customer. They can also send an invitation to their contacts asking "your birthday is coming please choose a gift on this portal..." The friend can buy the gift paying the whole price of the product and/or can put a part of the money as advance. For example if a gift price is 250 a customer can buy it or pay for a "piece" putting an amount chosen by him for example 50 and other friends can add some other money to that product. Then at the end of the period the Customer can eventually pay the rest of the price and buy the product. All users can invite to use the system their friends by sharing on social media and also via email. The system should be very user friendly with a nice and clean layout