^Man how long how this guy been playing, to have materials in the 100s.

Just play, farm, and not having the servants to use those materials. A few years ago, I have like 300+ unused stakes due to not having servants that use Stakes (Ereshkigal, Okada Izou, Charlotte Corday, etc).

Btw, I play since October 2019, so it's been 4 years since then.

Yup, sometimes you will gather a few hundred of some materials because your current servants don't need them, then you get some that do and Boom, all gone.