I visit the Yamotsu mines and allow my pet to cast on a shadow element. There is a way to force your pet to only attack with spells, as long as another pet is tanking the elly. This method works especially quickly, because your pet will be able to cast indefinitely without a delay between targets. Here's the secret:
1) Cast a line of energy fields between your pet and the shadow element, so that your pet is not able to reach its target.
2) Tell your pet to "kill" and target the shadow element. Unable to reach the elly with its physical attacks, it will begin casting.
3) Tell your to "stay." When the energy fields disappear, your pet will remain stationary, continually using its mana supply.
I'm not aware of any faster way to train a pet's magery, meditation, and evaluating intelligence.