Playing the game I'm doing because it gives a lot of gems

There are a lot of games like this, so I thought I'd just do the exploration and hidden quests and then stop, but it's better than I expected, so I'm sticking with it. I'm focusing only on raising my castle level to get the hidden quest rewards. Even though we're both level 20, my combat power is quite low, so I'm diligently trying to catch up.