How to learn values?

Hey guys! I used to play Royale High from around 2017-2021 but then quit. I've recently started playing again and I'd like to get into trading again! But, I don't know values anymore 😭 I was wondering if there's any kind of value website to help me in trades?? I don't want to accidentally end up poorer than I already am, and I also need advice on what's the best way to farm diamonds! I currently only have 72k, if anyone could help me out I'd be very happy and thankful 🙏🏻