Plugin Recommendation

Hi! I currently have a shop for gift boxes. I would like to make the purchasing process easy for my customer. These are the steps required:

(1) Choose a gift box
(2) Add in any items from my store

For easier visualisation, I would like to do it like the following site: foxblossom.com/pages/build-a-box where my customers can easily add the item to the top bar once they click “add to cart”.

Any recommendations? Thank you!