Need Help With My First PC Build for Casual Gaming

Hey everyone! I'm a beginner looking for some advice on my first PC build. I'm feeling a bit overwhelmed trying to compare different components like CPUs and GPUs. I aim to use my PC mainly for casual gaming and occasional streaming. I plan to play games like Minecraft, Elden Ring, Dead by Daylight, and League of Legends. I've put together a build [here](https://pcpartpicker.com/list/b9Bdcx), and I'm looking to buy most parts used. However, I've heard it's not a good idea to buy the motherboard, memory, or power supply used. My budget is around $500-$800. Any tips would be super helpful, and I'm also unsure about what case to get. Thanks a bunch!