This is a simple calendar I put together to show when and what to design and list on eBay. There are no hard and fast rules about when to list but I hope this helps you to get ready.
JANUARY: Start selling spring-transition items. Short sleeved with wraps or jackets.
Wrap up Valentines Day oufits and start
FEBRUARY: Keep selling spring items and Easter items.
MARCH: Spring & summer-transition.
MAY: Summer & start 4th of July outfits.
JUNE: 4th of July & summer
JULY: Back to school, fall items
AUGUST: Back to school, fall and Halloween costumes
SEPTEMBER: Halloween & fall
OCTOBER: Still selling fall & introduce holiday outfits.
NOVEMBER: Clear out all fall & winter items
DECEMBER: Consider taking a break and enjoy your holidays. If you must list then do some simple sets and Valentines Day sets.