You might be better opting for an umbraco ecommerce plugin such as Cartbraco. Its cheap, easy to use - adding a buy it now button is as simple as adding this one line of code to your razor template:

@await Component.InvokeAsync("CartbracoBasketSummaryVC")

Adding a basket and checkout is as easy as this:

@await Component.InvokeAsync("CartbracoBasketListVC")
@await Component.InvokeAsync("CartbracoCheckoutVC")