It sounds like you are doing online garage sales, selling personal property items (not business or hobby income). In this case, you only need to report items you sold at a gain as you cannot deduct losses on personal property. You probably don't have enough gains to generate a filing requirement.
However, if you receive a 1099-K, you will need to report it for any items that generated a gain. TurboTax can easily handle filing a tax return for any 1099-K you may receive.
Personal Items Sold at Yard Sales Only items you sell for more than the original price you paid have to be reported.
Reporting a 1099-K for Personal Item Sales