I don't register for anything if I can help it and I don't expect you to either. I'll need a shipping address plus I'll need an email address for us to be able to communicate, but I do not ask you to create an account and you won't need to login to make an order.
Most of my clients use PayPal and for that I need the email address associated with a PayPal account. However if you want pay me with BitCoin, wire the money, bring me cash or whatever, I don't care, as long as it happens. Likewise, you want your merchandise on time and as ordered, and fair enough. I will do everything in my power to make you happy.
No cookies will be stored on your computer and I will not track you in any way. Nothing you tell me will be shared with anyone other than those that require it (such as a shipper). You will not need to put your first-born up as collateral. My uncle was not, is not, nor will he ever be a Nigerian minister of anything. I promise.
Now, I'm a salesman, as no doubt are you, and you know as well as I do is that the best business is repeat business. With that in mind I would like to be able to contact you in the future. But I do not require it, plus I will be clear and upfront about it and you can opt out at any time.
I want this to be just like buying and selling at the mercado (local market): Simple, tidy and profitable for all.