First, thanks for the feedback and suggestions! Only then can we improve our game more and more!
Answering your questions...
1 - As we are at an early stage, significant changes happen between one version and another, and one thing or another is unbalanced. The stamina system started working now in version 0.4.0. It made it possible for the MC to perform a lot more actions than previous versions (and consequently accumulate a lot more money). Before in the first week, it was tough to save some money and still pay the father, so it was very cheap. Now with the evolution of the game (and the stamina system), the amount of crop fields is really low (we can increase it), and you can accumulate much more money. We will review the debt amount for the next version. Remember that we are also implementing new tasks, and probably fishing will be available in the next version.
2 - About the gifts. It might be a good idea not to lose the gift. The girl can decline... I will open a poll in our discord community to check this question! And we will also try to improve the girls' feedback when you give a gift. As for clues, we also have plans to add more information and tips via other NPCs in town (we will add more NPCs in town in the next version). And we working to improve the conversations with the girls, so, they can give hints.
3 - Yes, the gem system is implemented, but gems are very rare, and the chances of dropping are very small (1%). We may have to balance this in future releases as well.
And again, thanks for the feedback!