I am still young, so my suggestion might not be as experienced. I consume vitamin c and calcium to build stronger bones. I also drink collagen. It tastes orangey and berry. (brand K Colly)

For my face and skin, I use lactic acid to micropeel. That whitens the skin.

Micropeeling is good. You can do it at home.

Botox can stay up to two years, however it will make your skin stiff. You will also experience slight discomfort on the area injected. It definitely does not look natural on old saggy skin.

I think face or necklife is good.
However, you can opt for neck liposuction at younger age so when you are older you will not have much saggy skin beneath your chin.