As said before, your ego is directly related to your main stat and Alpha girl. I am pretty new, but found a pretty good battle strategy. I have found it is best to focus on both main stat and attack. I look through my harem to find the girl with the highest stat matching my main, Know-how for alpha and maximum ego. Then I click through all girls for my beta, watching my different stats go up or down to see how they affect my attack, and pick the one who gives the highest attack, then click through again to find my omega watching attack again. It depends on your mix of girls, how you give them experience and affection. I attached my current top stats below. I have higher level girls that aren't my main stat, but they don't give me higher stats even in their specified main, or attack. That could be because Mizuki is Legendary, and Rumiko is maxed out currently. I use this team in the tower of fame battles, and I use girls that I want to earn experience and affection in the arena battles.