When you're first starting out and not doing very many sales, having a mess of things probably won't affect your eBay business too badly. However, when you start ramping up sales to the levels of a PowerSeller, organization becomes a must.
If you are unorganized, running your business will require more of your time. Time that you could be spending doing what it is you would rather be doing, or time that could be spent making even more money!
One of the most time consuming parts of your eBay business will eventually become preparing and packaging items for shipment. The more items you end up shipping, the more important having an efficient system becomes.
During one of my busiest times as a PowerSeller, I received payments for around 70 items in a single day. But by utilizing an "assembly line" type system, I was able to package and print labels for all 70 items in about 4 hours.
Had I not utilized the assembly-line system, the time it took to package and ship could have easily taken me 6 or 7 hours. As you can see, your level of efficiency has a direct effect on your pay versus time.
Your assembly line does not need to be complex. It can be quite simple or very complex -- whatever you need to suit your specific needs.
I had a long counter where I did all my packaging. On one end was a stack of shipping boxes and padded envelopes. By taking a step or two to the right, you'd run into a bag of styrofoam peanuts. Another step or two to the right and there sat my packaging tape on a tape gun.
After checking orders in the morning, I would print shipping labels for all the auctions I had received payment for, which most types of auction management software can easily handle. I would then take the stack of shipping labels over to the boxes.
With experience, I quickly learned what size box I needed depending on the order. The first thing I'd do is attach the shipping labels to an appropriate sized box.
Next, I would place the first item into the first box. Taking two steps to the right, I'd secure the item by filling all the empty space with styrofoam peanuts. Two more steps to the right and the box was taped up.
Back to the start and to the next product. This would continue until all items were packaged.
If you don't have a counter like I did, a long table often suffices. Packaging materials can easily be stored underneath the table for easy access.