What is important in After effects? GPU? CPU? RAM? Hardrive? Which one should I buy?

‌In order of priority:

1. CPU. At least a 4 core with hyper threading but preferably 6 or 8 cores.
2. RAM. At least 32 GB.
3. SSD for media and projects and another SSD for media cache.

The video card is completely irrelevant. AE does not accelerate anything apart from the 3D Ray tracing and that is being phased out. Second, the latest nVidia 900 series do not support Ray tracing acceleration and AMD video cards are out anyway, since in PR they are around two times slower than nVidia cards.

See Tweakers Page - What video card to use.

Hi there,

All of them matter actually;

CPU - for multi-threading options

GPU - helps in ray-tracing calculations

RAM - faster previews

HDD - I'd recommend SSD - the faster the drive the faster projects can be loaded + more disk cache can be allocated

If you have priorities, I'd suggest - 1. MultiCore CPU, 2.RAM (At least 16GB), 3.Good Graphics CARD, 4.HDD/SSD

Hope this helps! :-)