Admin can create various gift products.
Admin can create various gift Rules based on the order total value, buy x get y
A separate page to show all the gift rules.
The gift product will be automatically added in cart of the buyer.
The buyer can replace the gift from the list of free gift available.
Gift on order by webkul will enable you to assign free gifts with order, as per the rules defined. To display the gift on frontend, the first step is to select the product you want to add as a gift - by visiting the product section of shopify and choosing the gift on order from app section. You can then create the rules to assign the gifts, set up the minimum order value to become eligible for the free gifts.
A pop can be added on the home Page, so the customer is aware about the gifts.
front end view
cart page rules
gift on order app home page