What I’ve learned about the care of gouldian finches is the result of research. There are many wonderful informational websites out there to learn from. When it comes to what constitutes the best diet for thriving finches, the opinions vary. Every breeder’s feeding regimen will vary in the details, but there are definitely some basic essentials.
The staple of any seed eating finch’s diet should be a good quality seed mix.

Fresh millet should always be readily available for grazing.
In treat cups my birds always have an oyster shell and carbon mixture as well as a dried herb mixture. The carbon aids digestion, the oyster shell provides calcium, and the herb mixture is a treat that also provides self-medicating benefits for the birds. These things are inexpensive and last a long time.
Supplements can be added to soft food, sprouted seed, or drinking water. I give fresh soft food everyday along with chopped fresh greens -- kale, collard or turnip greens or green leaf lettuces are some good choices, but spinach should be used only occasionally and never iceberg lettuce as it has no nutritional value for the birds.
My birds feed a combination of seed, millet, soft food and greens to their babies, so the supplements also benefit the young directly.
*******************************************************************************************************
2 hard-boiled eggs
1/2 cup dry egg food
powdered vitamin supplement* (check the proper dose for the supplement you’re using)
1 cup finely chopped fresh greens
1 cup fresh or thawed sprouted seed

Peel eggs and shred into bowl. Nuke egg shells for about 30 seconds and grind into powder. Add egg food, vitamin powder and ground egg shells to shredded egg and mix well with a fork.
Keeps in refrigerator for about three days once mixed with sprouted seed and chopped fresh greens.
*There are many to choose from, so do your research -- I am currently using a product called Breeders Blend which replaces all other vitamin supplements and meets the birds nutritional needs year round.
******************************************************************************************************
There are many ways to sprout seed for your birds, but after much experimentation, this is the method that works best for me. Sprouting the seed right in the mesh bag makes frequent rinsing very convenient and the bags are easily washed.
I generally mix canary seed, white millet, and japanese or red millet for sprouting. Other seeds can be used, but some of the oilier seeds, once sprouted, don’t seem to keep as well in the fridge.
Mix the dry seed in a fine mesh bag and rinse well.
Soak for 6-8 hours, rinsing once and replacing the dirty water half way through.
Rinse VERY well and drain.
Lay the bag on it’s side in a foil or other flat pan and flatten it gently.
Cover, leaving one end slightly open for air and leave over night.
Rinse well again and drain. Place bag back in pan, rinsing once or twice a day until sprouts begin to show - this should be 24-36 hours depending on the freshness of the seed.
Keeps in refrigerator for 3-4 days.
I sprout lots at a time and store it in the freezer, thawing it as I need it.