You need to provide a professional service, imagine what service you'd like from M&S online, for instance. Be scrupulously honest about how much you have used things & how worn they are.
Women's clothes are considered the nightmare items that buyers moan about & pay a pittance for. If you must sell women's clothes, give every measurement you can & be painfully honest about every single sign of wear.
Buy it now is better than auctions (more attractive, gets better prices).
Research what similar items have sold for (use advanced search/Sold option).
Only list for a price you can bear to see it go for. With Buy It Now, I often list for 30 days for what I think is a stupid high price. Then relist a bit lower the next time (if it hasn't sold), etc.
I list stuff with postage costs included so buyers can't moan about that. You need to research best cost options so that your list price gives you a profit & pays for Ebay fees (14%) & covers delivery charge.
YOU are responsible if item doesn't arrive. Back to M&S standards of customer service.
I only send recorded for items worth £10-£20 or more. I very rarely have to claim from Royal Mail using that strategy (but claims have been easy enough for me).
Take the best quality pictures you can. Show any problems clearly.
Sorry if that's complicated. There is a learning curve. Not very steep, but real enough.