You can't really get Castle Story for free. Such attempts might lead to legal troubles and could also expose your device to risks like malware or viruses. Just buy the game and enjoy it without any worries.
One way to get free gems in Castle Story could be by completing daily quests. These quests are often designed to reward players with various resources, including gems. Another method might be through achievements. When you reach certain milestones in the game, like building a specific number of structures or reaching a particular level, you may receive gems as a prize. Also, keep an eye on in - game events. Sometimes, special events offer free gems as participation rewards.
You might find some unofficial and potentially illegal ways, but I don't recommend that. It's best to purchase the game to support the developers and enjoy a legitimate experience.
You can often get free coins in Castle Story by completing daily quests. These quests are usually simple tasks like harvesting a certain number of crops or building a specific structure.
I recommend a light novel called "The Infinite Castle from the Apocalypse". Although the male protagonist was not Arthur, the protagonist in the story also owned a castle. However, there was no cook, no guards, no butler, and even more hateful was that there were no maids! However, the protagonist had many different identities, such as the girl's friend, the prince of Frerzord, the overlord of the four seas, and the strongest ninja in Ninja World. In this novel, you can see exciting storylines and rich character settings. I hope you like my recommendation. Muah ~
One way is to base it on the existing blood - related mechanics in the game. Maybe a character discovers a new form of blood transfusion that has the power of 'Blood for Blood'. They could use it to either heal themselves by taking the blood of their enemies or gain new abilities. This would add an interesting twist to the fanfic and stay true to the game's themes.