I think your idea of opening a Shopify store is a great one! People love shopping online, especially second hand. Do you have an Instagram account that you can post items on and use relevant HASHTAGS so customers can find you? I am a stylist and shop at lots of second hand stores via Instagram. Use the tag #circularfashion and check out what the likes of ‘Hattie’s Wardrobe Green’ and ‘welcomeback_slowfashion’ are doing. Another great NZ charity doing this well is ‘everlasting_recyclingwithlove’. There is a want for your product out there and if you push the charity element people will be even more keen to support you. Best wishes!