I have over 5 years of experience executing e-commerce start-ups. My friend, I will try to help you frame a vision for your challenge, though your questions are somewhat reverse ordered in hierarchy of importance.
You have vaguely defined your area of interest as "artsy". You need to find a niche within the "artsy" ecosystem or industry where you can offer real value. First of all, you need to know who the present dominant players in the artsy market are, their strengths and wekaness( what are the areas where they are satisfying customers and what are those areas where they are not doing well). You might want to pitch your tent at their weak points and those weak areas usually make them unresponsive to "small orders" or "common" consumers. If you can do this successfully, then you can begin your Product Conceptualization. You need to develop your product or service along these areas, e.g. better distribution network, more affordable logistics, etc.
The second question borders around SOURCING. There are myriads of ways to achieve this in an age of internet. You can source via Alibaba, eBay, etc. Your guiding principle in sourcing should be ARBITRAGE. What source would offer you a price advantage to compete locally? For instance, if an artifact would cost less to import from China, why would you source for it in America?
When you have sorted those two critical factors of Product/Service and Sourcing, then you begin considering the e-Commerce PLATFORM to use. I believe you want to be in business not for the fun of it but for some benefits or profits, then you might consider starting off on more affordable platforms like Alibaba.com or eBay where your setup costs will be very low. Create you profile there, advertise your products and when you have secured sufficient "follower-ship" , then you can seek a web portal(based on your business profitability) to showcase your business. Now , you can look to Wordpress + its ecommerce plugins and get a developer to setup your ecommerce site.
Let TECHNOLOGY enable business and not the other way round. Always have your BUSINESS STRATEGY in place before seeking TECHNOLOGY PLATFORMS to fulfil it. Understand the VALUE CHAIN in your particular "artsy" industry and then explore the "technology interfaces" to help you connect among the various "value" players from "upstream" to "downstream".
You can call me for more clarifications.