I have found 3 main feed items.
1) Sunflower Hearts - mixed seed just gets thrown out of the feeders until they can get any sunflower hearts that are in there.
2) Dried Mealworms - Almost all birds seem to love these, but they're not cheap, and the starlings will empty a feeder in under an hour. So I have replaced them with fruit & mealworm pellets which are cheaper and are not quite so easy to eat so they last longer.
3) Fat balls - again most birds like these, and depending on the time of year, they sometimes get emptied before the seed feeders.
I have found that peanuts and Niger seed are both left to rot in the feeders, so I no longer buy them.
The one most important thing I have found that gets birds onto the feeders is cover. They don't want feeders sat in the open. Mine are about a metre from an 8ft hedge at the back of the garden, and sitting between an apple tree & an Acer.