Where can I find guide/tips to play the game?

The game has a wiki
https://calderiagame.fandom.com/wiki/Great_Houses_of_Calderia_Wiki (新しいタブで開く)

We have also made a video to help you understand the basics of the game:
https://www.youtube.com/watch?v=jrwe2qTxMnU&t=5s&ab_channel=FIRESQUID (新しいタブで開く)