i use store bought crickets usually. you can get them in different sizes for different sized plants, they're relatively cheap, and easy to aquire (just go to a pet store). i just bring them home, throw them in the freezer for a while, them feed them to my plants.
i also use dried blood worms. just dump a small amount into the pitcher and your set. these are also available at any petstore.
in the past i have tried blood meal, hard boiled egg whites, 2% milk, hard boiled egg whites, protien drinks, even ground up herbal suppliments (bee caps).
the crickets and blood worms are by far the easiest and best in my opinion.
tech...