The easiest thing to invest in would be the fest items, do what you can to save up Fest currency so you can buy multiples of the new fest item and the familiar, then wait and check the AH to see what they’re going for and list your duplicate items when you see a nice price. Depending on how long you can/want to wait for things to sell will determine how much you should undercut. for example, want to sell something currently priced at 250g quickly, undercut to 200g-220g, if you’re willing to wait, either price it the same as the current price or undercut by 5G