To use After Effects, Maxon C4D, Octane and Redshift at high power, you will need a GPU that has CUDA-Cores, meaning you will need an NVIDIA GPU. VRAY-RT additionally supports OpenCL meaning you could use an AMD card here. Indeed we will reveal you the best gpu for rendering.
The best bang-for-the-money NVIDIA cards are the NVIDIA 2070 RTX (2304 CUDA Cores, 8GB VRAM), 2080 RTX (2944 CUDA Cores, 8GB VRAM) and the 2080 Ti (4352 CUDA Cores, 11GB VRAM).
On the high-end, the currently highest possible performance is offered by the NVIDIA Titan V and Titan RTX, that also comes with 24GB of Video RAM.
These Cards though have worse Performance per Dollar as they are targeted at a different audience and VRAM is very expensive but not necessarily needed in such high capacities for GPU Rendering.
GPUs, that have 12GB of Video RAM and more, can handle high-poly scenes with over 200 million unique objects best. Take a look at the performance per dollar tables below, though, to get an overview of how expensive some of these cards can get without offering that much more performance.