Add my own added to checkout system

I have my own products with my own buttons and when you click buy now it takes you straight to the 2checkout ( plug and play ) system.
There is a button at the top of their checkpout that says continue shopping but it’s not clear I think people may think they have to buy once there.

I don’t want a shopping cart ( as I already have my products and don’t want to add additional address / shipping forms etc ), I just want to be able to add to a cart when they click and have an image like a bag at the top which shows the additions that they can click when done which will then take them to the 2checkout…

I’ve done some searches, i can only find full shopping carts, how do I add my own simple added to cart image / system?