I can't comment on the brain tumor friendly part but here are some of my favourite things.
Centrum multivitamin supplement. I take it all winter every year. Then if I feel run down I add in the soluble vitamin C + zinc tablets, any brand will do.
Drink lots of stuff that isn't fizzy and doesn't contain any caffeine. So fruit juice, squash juice, herbal tea, water etc for hydration. Avoid alcohol. I believe all the "bad" things are dehydrating.
Vichy Mineral 89 serum daytime and Estée Lauder Night Recovery Complex serum nights.
Face oil next, currently using Garnier Organics Hemp Oil, love it.
Simple moisturizer doesn't irritate the skin and they also have a SPF 30 moisturizer which I put over the top of a plain one.
Currently using Clarins SoS Primer in pink (the anti fatigue one) which adds a pinky sparkle to my skin.
Followed by Maybelline Dream Radiant Liquid foundation with hyaluronic acid and collagen, which I think should be relabelled "hyaluronic acid serum with a tint". It doesn't sit in lines, is very sheer and doesn't feel like you're wearing foundation.
I use a pale silvery pink eye shadow on my kids to brighten them and mascara to open up my eyes (my glasses tend to make them look small) and finish with nude lipstick.
You sound like you might need to add some blush too, I believe cream is less likely to settle into lines than powder but have never tried it. It's possible to put on only the tiniest amount of blush so it's not noticeable you're wearing any, it's just you suddenly look healthier once it's on.
Olive oil for an intensive hair moisturizer and a haircut for the brittle ends. It's hat weather so I wouldn't worry about the patchy situation. My hair is mostly braided and covered with something all winter. I like hooded cardigans, and berets too and since they're part of the outfit you don't take them off indoors, could that be an option for you?