Try to use the energy as soon as it is accessible. By allowing a full energy bar to sit you run the risk of surpassing the needed amount of training to reach the next level and missing out on gaining more with the passing time.
One training goal is to raise level. When the next level is far away in number, train in highest confidence category. Train in lowest confidence when the next level is close at hand. If "to next level" is under ten, take the chance to train a confident category with the energy while available.
Leave one or two categories low, focus training till superior in minimum of 4 categories. By focusing on only two categories is unlikely to balance 4 weak categories in battle. If "to next level" is under ten, take the chance to train a confident category with the energy while available. Use battles to determine where training is needed. Disregard the category/ies that you are allowing to be weak, and don't forget to add in Ability modifiers.
Having a low battle rank pits us against what is likely to be a lower leveled monster. The opponents are not always low leveled, and may be significantly higher leveled by ignoring the official battle to continue with the current rank while level progresses. This would increase that high level/low ranked monster's chances of winning. What is the benefit of this strategy compared to advancing in rank?
How are current rank and level affected when breeding? Would they decrease if one parent has less training? Is there a way to raise either by breeding? Would 'normal' or 'neighbor' choices make a difference?