I refer to RAM, GPU, CPU, I want to know which is the most important component to invest more in that than in the rest, I want to sculpt fluidly since that's more fun.
CPU(most important to frequency) and RAM(not that relative).
Yet, Blender is open source application, and it might not be a really good one to do specialize job like sculpting.
The things you referred are not the most important thing in fluidly sculpting. Most of the time, a good algorithm and code structure will make a huge difference. And those good thing is not likely include in Blender since there is too many aspect Blender need to care about, and there is not that much resources Blender Foundation can use to develop it.
If you really need and want to have a good experiences in sculpting, try some specialized application, e.g. ZBrush