What would be an acceptable/good CI range to strive for?
There is no acceptable level of CI below which there is no risk. The deleterious effects of inbreeding (described in a previous answer) increase in magnitude as the CI increases from 0%. Because of this biological reality, breeders should be aiming to arrange matings so as to minimise the CI of offspring. In other words, breeders should be aiming to arrange matings between animals that are least related.