For anyone else who is selling on Poshmark, Mercari, eBay, I thought I would share my favorite shipping supplies! I love to bulk buy my clear packing tape and save $ by buying multiple rolls at once (Costco style).
These tape rolls can run out quickly so a lot of people opt for a Thermal Printer:
For packaging, I have linked some cute polymailers, but honestly my favorite shipping supplies to use are the free supplies available at USPS.com
Finally, when you need to carry all this stuff down to your lobby or your car and/or walk to your nearest post office?! Check out these foldable wagons (which obviously can be used for groceries, packages, shopping bags, picnics/BBQs, etc!).
Hope this helps and let me know if you have any questions in the comments below!