Joomla and Hikashop. Yes, it is more work to set up than simply using shopify, but you are independent, you are flexible, it is cheap and when something like GDPR comes around the corner that prevents a system like shopify (or shopify is bought by Amazon or similar) you still have your shop. It is also Opensource. Also, if you are selling stuff that might be against the terms of shopify, your shop might get deleted, but not if you role your own installation. Definitely don't invent your own shop system, but use your own installation and an opensource solution.