What critical factors should I meticulously consider prior to embarking on the journey of constructing my online store? As I contemplate the various aspects, should I prioritize the selection of an appropriate e-commerce platform that seamlessly aligns with my business model? Furthermore, how essential is it to engage in market research to discern my target demographic’s preferences and purchasing behaviors? Are there specific design elements that are pivotal in creating an intuitive user experience that captivates potential customers? Additionally, what role does mobile responsiveness play in today’s digital landscape, and how might it impact customer retention? Should I also be cognizant of the myriad payment gateways available, ensuring a frictionless checkout process? And what about establishing a robust marketing strategy to drive traffic to my store? How can I effectively integrate social media and SEO tactics to elevate my brand’s visibility in an ever-competitive marketplace?