By putting bread and bits of meat on the garage roof you're doing the best you can to attract seagulls and magpies. Seagulls love swooping down to scavenge bread, and magpies eat carrion, and that's what you're providing, so my advice would be to stop doing that.
Then do as hypercharleyfarley suggests and hang feeders in a sheltered spot, near some bushes where the small birds can take cover if a sparrowhawk appears.
I find that birds cannot resist the white sunflower hearts so I have one tube feeder with those in, and another with mixed seeds and another with a mix for soft-billed birds (insect eaters like robins and wrens). Blocks of fat with insects in, hung in a wire container attracts Gt Spotted Woodpeckers and members of the tit family
Provide a constant supply of fresh water in a birdbath or large plant saucer on the ground with a stone in it for small birds to perch on.
Clean the feeders regularly and keep them topped up, sit back and be patient.
They'll turn up.