If your shop lives in DMs and WhatsApp chats, you are probably packing orders on the dining table between replying to messages. Packaging has to be quick to use, easy to keep in a cupboard and good enough on camera that customers want to post it.
You don't need thousands of boxes to look established. Printed courier bags start at 100 pieces and mailer boxes at 50, with no setup fee. Pick one or two sizes that fit what you sell, and add more once you know which products move.