It depends on what your budget, space and dedication allows
Dwarfs, are the preferred species and can be kept in a 10G
red eyed, and red eyed red tailed are a little bigger and more aggressive and can be kept in a 20G
South American Puffers, a personal favourite of mine, are quite sociable for puffers and grow to 6inches
then you have the much bigger puffers like the mbu which reaches length of 2 feet +