For me a mixture of stuff. For crafting HQ matters, minions, stuffed characters, housing items and glamour items all sell. I don't worry about looking for the highest price stuff but items that tend to move. I rather sell 5 items 5k quickly that one for 25k that takes a week. I will also use excess tomestones to buy crafting materials and sell those on the MB. Same for marketable dungeon/raid gear. I also saved money by not purchasing items I could get from vendors with gill or seals. A lot of these end up on the MB for higher prices than you can buy them at the vendor for. You mention you have an FC house so look into gardening. Gardening not only supplies exclusive items for crafting but things like Chocobo foods which sell well to players leveling their Chocobos or changing their color. The last thing that comes to mind is the basket in the Doman Enclave. I go there each week to sell stuff I plan to sell to a vendor to get the higher price.