First of all: what version do you have? This could determine the best way to get another character. Gozarutchis are, sorry to say, the worst care character out there. Taking better care of your tama is the best way to avoid a Gozarutchi for almost all the tamagotchis. If you're dealing with a TamaGo, however, getting Gozarutchi is based on low skill points, so if you're dealing with the TamaGo, try raising the training points by catching when it goes to the bathroom or cleaning up after its made a mess. Hope this helps, and good luck getting the characters you want!
xoxo,
Missvioletchi