Should be able to add multiple items with a +/- for item additions/removals. To reduce clutter, the list should be collapsible if possible when viewing the list of trade offers.
Additionally, one should be able to post the range of acceptable items for trade when making an offer, which should also be collapsible (and disable making duplicate offers for the same items/gold/lps). This would vastly reduce clutter and add to the readability/usability of the marketplace.