That largely depends on render engine you're using or have plans to use in the near future. If renderer of your choise uses CPU only, then naturally CPU have tobe the most important part in your PC. Respectively, if renderer uses GPU, then look for a best GPU you can afford. Then there are renderers that uses both, CPU and GPU...
In case of CPU rendering, RAM is important too. Novadays 16GB is bare minimum. 32GB is standart and sufficient for most situations, unless you're working with very large and complex scenes. Memory speed isn't very important for rendering AFAIK.
Data storage: 256-512GB SSD for OS and 1-3TB HDD for data.
Good reliable PSU and CPU cooler are needed too.
If you provide more info, like budget you can spend, then someone probably may come with more comprehensive list.
Good luck!
