Constructing a business website need not be expensive, complicated or time consuming.
Shop specific sites, like Shopify and Ecwid are mostly self contained with payment gateways and an easy to negotiate control panel. Linking a site to Ebay might also work for you.
For a more complex proposition a bespoke site can be constructed to your requirements.
Building a business online.
Marketing, social media and Facebook, like it or loathe it, it certainly can help. Email shots via Mailchimp (for example) are a cost effective way to keep a market engaged. There are plenty of options, it is just a case of finding the right combination.