u should just start a colony. Start with 6 adults, that will get u about 300 babies. 3 weeks later, as your eggs are hatching, buy more adults and save 6 to breed. Keep that rotation, till u have your own adults. And remember, breeders still become food. Let them sing and breed for about 10 days, them toss em in. I have the same food delema as u. I use canned crix for in between runs to town. I have 600-1000 baby crix, and 3 week old ones I feed in mass, this thins the herd a little.
A can of exoterra black crix is about 8$, but they are big and when frozen will last u almost 2 months. That is if it's your primary food source for just 1 frog. If used in just a pinch this can could last 4 months. Canned food is better than no food. U can start feeding them nightcrawlers, as this big meal will hold them longer.