Wait for it to go even lower to be honest. It appears to be a good buy, but, you don't really want to risk it. Best thing to do is buy little amounts, say like around 5-10 of items that you think will make you a profit, the first few times you try merchanting, to see if you are correct in your judgement. Once you're satisfied with your ability to judge whether you'll make a profit on the item yourself, that's when you should buy larger amounts. ;]