Find a local agriculture co-op and purchase a fifty pound bag of birdseed. Costs about ten bucks and will last the whole year within contained feeders. Don't need to spend any money on birdfeeders, either. The birds won't complain a whit if an old 2-litre soda bottle is drilled for perches and seed ports and hung upside down on a handy tree. For the cost of the seeds, the birds will take care of all the bugs.
Grasshoppers are especially tasty treats for the birds.
They love grubs, spiders and crickets as well. As an added bonus and for no additional charge, a robin might hop along with you while doing garden chores, assisting with worm disposal, though this is normally not a big problem for a gardener. To further encourage the birds to hang around, put up some birdhouses. Most any rain tight container with a perch and hole for access will do. Again, there are many books on the subject, also for free if you frequent your local library.