They should be breed no earlier than two years old. Gouldian
finches are known as bad parents and they are likely to
abandon eggs and chicks. This is not to discourage you but to
inform you. Also it is wise to have a pair of society finches
on hand just incase trouble rises. Now it depends on the bird
but from what i have read they need time to adjust to the food
and may take their time to try knew foods. But just keep
feeding them the yummy foods like greens and chopped carrots
occassionally some chopped fruits and nuts and egg food. Also
if you supply the nest with the material already inside they
will like that and will kick out the stuff they do not need.
They seem to prefer half opened nest box lined with fine
grasses. My finches personally like green and white material
and sometimes cotton, toilet paper and alfalfa and some others
i can't think of. Well good luck!