For what it's worth, I have a few feeders up with different kinds of seed. The black oil sunflower feeder is bar far the most popular, attracting seed eaters both on the feeder and below. Suet is predictably popular and gets 4 species of woodpeckers on some days along with a wide variety of passerines.
Farther away from the house I have a feeder which gets Tractor Supply's "Value Mix' bird food which contains a mix of "milo, white millet, cracked corn, wheat, black oil sunflower." This feeder gets more action from the towhees and song sparrows than the sunflower only feeder. The mix is fairly heavy on the milo, but it seems to mostly get eaten as there is a fairly small amount of uneaten milo on the ground below.
My least used feeders are the ones containing nyger (aka thistle) seed. I'll see an occasional junco taking a bite, but it has failed to attract the neighborhood finches in the 8 months we've lived here. At my previous house I only got goldfinches as the nyger feeder in spring, so perhaps that trend will continue.
If you live near a Tractor Supply, they have the best prices I've ever seen for bird food. Black oil sunflower is $19 for 40lbs and often on sale for a few bucks less. Their "value mix" is $9 for 35lbs and contains a surprisingly high percentage of black oil sunflower seed considering the price.