>>6176123Try listing a few of your cheapest things first so you don't blow it when it comes to selling the stuff you'll make the most from. Plus, you'll get some good practice. Doing this might help you with knowing how much shipping will cost, too.
I started off using flat-rate boxes (I assume you're in the US?) but they can cost a lot (I think the shipping rates for the small is about $5, medium 8 or 10 or 12, and large about 15). The USPS offers free delivery of many types of their boxes to your home, which I find very handy. Specifically, their website has a sampler pack of their flat-rate boxes, but you can also go into any/most post offices and get the boxes there. Try out the different sizes and if you find a size that works for what you're selling, then you can order them off their website, sometimes in packs of up to 25. I use the regional rate box a2 (10.9375 x 2.375 x 12.8125) a lot. When I last sold I think the shipping would be about $5 for each box, but I could be wrong and the price could be very different now.
Luckily for you, eBay actually is pretty good when it comes to shipping, if you can figure out the odds and ends of weights and box sizes and what not. They used to give sellers a discount too, hopefully they still do.