Advice/tips on better self care/health?

Hi! So I am 28 and have 2 daughters, and I live in California where summers get into 115-120° F often enough.

I’m needing some help on learning how to take better care of myself as that was never a thing in my family. My diet isn’t the greatest, and that is slow to change due to my own food issues, and I have anxiety.

Most of my life I was fairly underweight and have semi dark circles under my eyes.

But I’m not anemic, my most recent blood work showed I’m low in B12 but nothing else. I get heat sickness/exhaustion easily and am frequently tired throughout my day, but I also have trouble sleeping at night now.

I’d love any tips and/or advice on self care, skin care, vitamins/supplements, how to drink more water , and maybe slow ways to start trying out more foods. I know this is pretty generic, but I am at a total loss and overwhelmed.

My mom passed away in December and I really want to take better care of myself so my own daughters don’t have to worry about losing me and so I can teach them how to take care of themselves better.

Advice/tips on better self care/health?