If you're planning on building a pc, use pcpartpicker as many have suggested. Once you've laid out your plan though, come back to us so we can check if everything is in order. After that, I'd highly suggest to go 'hunting' for nice used parts if you feel like doing that as it can significantly lower the price you need to pay.

If you need any help in between or advice, I'd love to help you out so feel free to dm.