For me sunlight and some light exercise everyday were a game changer. I had tried Vitamin D supplements (1000 IU daily) before but there was barely any noticable effect.
> If you have brown/black skin it can be even more
My skin happens to be very light so sunburn is more of a concern. The evening hours are pretty safe though.
I was diagnosed with low VitD and they said I should take like 1k-2k, but I didn't feel much.