Help with custom package creator

Ok, I’m pulling my hair out trying to figure this out, but I’m not even sure what questions I should be asking.
I’m trying to create an app for my sales team to build customized packages for our customers. (we are a door 2 door company)
I have a sheet with a list of products in it with descriptions, pricing etc…
I create a simple card view that lists the products.
First challenge: I want to be able to add/remove products to an order from this view, with a +1 type button. I believe I should be adding lines of products being ordered to a sheet, with an order number attached to it so it can be reference for a breakdown of the order. But I cannot figure out how to accomplish this.
What would the best practice be to accomplish this?
In short:
Add products from a card view list of products
Review the complete order of all the products added to the order
Be able to update the quantities of products

Any help or direction is greatly appreciated. I have been watching videos but I am not sure what I should be doing to accomplish this and I havent found anything remotely similar.

The sample app below may not be exactly as you have envisioned your app. However it will certainly help you get idea of a typical AppSheet app set up that matches your requirement.