Building a website with max user experience

I want a website where people can buy stickers. The user can upload a photo or he can choose from a library of photos (API www.bigstock.com). Then he specifies the format and desired quality. Then the order is placed (payment gateway).
Maximum responsive design is required + standard e-commerce features + CMS for other screens to explain everything.
I am a webdeveloper myself (I can provide rough design). If this works fine, we can continue co-operation. Also app required in near feature.
Please convince me why I have to chose you. I want to be online with this website asap.