I found the cards do good as individuals but shipping is more in the long run at one at a time but theme auctions can do good like this one but I suggest you use a bubble envelope and use tracking for anything that goes high., I found playsets are hit and miss just control your start bid to help with making shipping cost worth it, I will watch and fan you good luck.
I understand I do the same but on individual cards I ship with regular envelope to cut down shipping cost just protect the card inside. Hope to see more auctions we need more sellers
the small flat rate box is 6.00 with tracking and the bubble wraps I usually spend 5.00 or under but envelopes don't have tracking but you can ship around 5 cards for one stamp
make sure the cards ar not loose in a envelopes my post office told me that USPS are cracking down on loose items in the mail because loose items like trading cards are breaking mail sorting machines which also damages other peoples mail and causes a pile up in mail system sorting lines. So now with large lots of cards they have to be wrapped and put in to bubblers or a small mailing box. Getting damaged cards is not a good thing and that is something no one like to get that causes issues are cards are always fully protected.