My mom supports all the birds in her neighborhood. Most birds like the mixed seed blend, it has
sunflower seeds, millet and a few other things and that will attract a wide range of birds. It takes a bit of time, bird of mouth if you will, for them to show up so not to worry!
Do try to look for the big bags of bird seed at Lowes or the like, some say they don't sprout and that's a good thing unless you like weeding underneath the feeder. Sparrows love this seed blend.
Also, a fun thing to try is the niger seed, you buy a special sock thing that has little perforations and you fill it with niger seed and affix it to a post or a branch. Zebra finches in my mom's neighborhood really dig it and the perch all over the sock in a frenzy pecking the seed out.
Lastly, if you live in a place where it gets cold, you can get these plastic trays filled with suet. Woodpeckers really like the suet and so do flickers and bushtits. the names of birds really crack me up, right? My mom has a seed feeder with slots on the end for the suet and the birds go crazy. the suet does not melt or make a mess and it's high energy for the birds.
My favorite thing to do as a kid was to spackle a pine cone with peanut butter then roll in the bird seed and hang up under the eaves of the house. Sort of a bird aerobic class to get them to perch on it while they peck.
As an non-birder, apparently I have learned a lot through osmosis!!