Zebra finches and Society finches are highly recommended for beginners. They both tend to be easy to care for and easy to breed (although individuals will vary). Zebras and societies come in many interesting mutations that can introduce one to finch genetics. Zebras tend to be more aggressive than Societies. Both are inexpensive and readily available. Zebras are easier to sex than societies, so it may be easier to get a true pair if you wish to breed.