The most important statistics to track in online poker are those that provide insight into your own playing style, as well as that of your opponents. This includes metrics such as aggression frequencies, betting patterns, and table dynamics, which can help you identify areas for improvement in your own game, as well as exploit weaknesses in your opponents. Additionally, tracking statistics such as win rate, return on investment, and volatility can help you evaluate your overall performance and make data-driven decisions to optimize your strategy.